Optical module

ABSTRACT

An optical module includes a mirror unit and a beam splitter unit. The mirror unit includes a base with a main surface, a movable mirror, a first fixed mirror, and a drive unit. The beam splitter unit constitutes a first interference optical system for measurement light along with the movable mirror and the first fixed mirror. A mirror surface of the movable mirror and a mirror surface of the first fixed mirror follow a plane parallel to the main surface and face one side in a first direction perpendicular to the main surface. The movable mirror, the drive unit, and at least a part of an optical path between the beam splitter unit and the first fixed mirror are disposed in an airtight space.

TECHNICAL FIELD

The present disclosure relates to an optical module.

BACKGROUND ART

An optical module in which an interference optical system is formed on asilicon on insulator (SOI) substrate by a micro electro mechanicalsystems (MEMS) technology is known (for example, see Patent Literature1). Such an optical module is gaining attention in that this opticalmodule can provide a Fourier transform infrared spectrometer (FTIR)realizing a highly accurate optical arrangement.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication No.2012-524295

SUMMARY OF INVENTION Technical Problem

However, the optical module as described above has the followingproblems, for example, in that the size of a mirror surface of a movablemirror is dependent on the level of deep drilling on the SOI substrate.That is, since the level of deep drilling on the SOI substrate is about500 μm to maximum, there is a limitation in the improvement of thesensitivity of the FTIR due to an increase in the size of the mirrorsurface of the movable mirror. On the other hand, when the movablemirror increases in size as the mirror surface increases in size, thereis concern that the movable performance of the movable mirror isdeteriorated or the entire module increases in size.

An object of the present disclosure is to provide an optical modulecapable of suppressing deterioration in the movable performance of themovable mirror and an increase in the size of the entire module whileenlarging the mirror surface of the movable mirror.

Solution to Problem

An optical module of an aspect of the present disclosure includes: amirror unit; and a beam splitter unit, in which the mirror unit includesa base which includes a main surface, a movable mirror which includes amirror surface following a plane parallel to the main surface and issupported by the base so as to be movable along a first directionperpendicular to the main surface, a first fixed mirror which includes amirror surface following a plane parallel to the main surface and ofwhich a position with respect to the base is fixed, and a drive unitwhich moves the movable mirror along the first direction, in which thebeam splitter unit constitutes a first interference optical system formeasurement light along with the movable mirror and the first fixedmirror, in which the mirror surface of the movable mirror and the mirrorsurface of the first fixed mirror face one side in the first direction,and in which in the mirror unit, the movable mirror, the drive unit, andat least a part of an optical path between the beam splitter unit andthe first fixed mirror are disposed in an airtight space.

In the optical module, the movable mirror includes a mirror surfacefollowing a plane parallel to the main surface of the base. Accordingly,the mirror surface of the movable mirror can be enlarged. Further, inthe mirror unit, the movable mirror and the drive unit are disposed inthe airtight space. Accordingly, since the drive unit moving the movablemirror is hardly influenced by the external environment, it is possibleto suppress deterioration in the movable performance of the movablemirror. Moreover, the mirror surface of the movable mirror and themirror surface of the first fixed mirror face one side in the firstdirection. Accordingly, it is possible to suppress the height of themirror unit in the first direction as compared with, for example, apositional relationship in which the mirror surface of the movablemirror and the mirror surface of the first fixed mirror are orthogonalto each other. Moreover, at least a part of the optical path between thebeam splitter unit and the first fixed mirror is disposed in theairtight space. Accordingly, it is possible to suppress the width of themirror unit in a direction perpendicular to the first direction. Asdescribed above, according to the optical module, it is possible tosuppress deterioration in the movable performance of the movable mirrorand an increase in the size of the entire module while enlarging themirror surface of the movable mirror.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a support body having optical transparency, thebase may be supported by the support body, the first fixed mirror may bedisposed on a surface at the side opposite to the base in the supportbody, and the support body may correct an optical path differencebetween a first optical path between the beam splitter unit and themovable mirror and a second optical path between the beam splitter unitand the first fixed mirror. Accordingly, the interference light of themeasurement light can be easily and highly accurately obtained.Moreover, a light transmitting member correcting the optical pathdifference does not need to be provided separately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, the drive unit, and the supportbody, the package may include a wall having optical transparency, thebeam splitter unit may be supported by the wall, and the airtight spacemay be formed by the package. Accordingly, both of the formation of theairtight space and the support of the beam splitter unit can be realizedby the simple package including the wall having optical transparency.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, the drive unit, and the supportbody, the package may include a wall provided with at least one openingthrough which the first optical path and the second optical path pass,the beam splitter unit may be supported by the wall while blocking theat least one opening, and the airtight space may be formed by thepackage and the beam splitter unit. Accordingly, both of the formationof the airtight space and the support of the beam splitter unit can berealized by the simple package including the wall provided with at leastone opening.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, the drive unit, and the supportbody and a support structure which supports the beam splitter unit, thepackage may include a wall having optical transparency, the beamsplitter unit may be supported by the support structure while beingseparated from the wall, and the airtight space may be formed by thepackage. Accordingly, since the support structure supporting the beamsplitter unit is provided separately from the package, it is possible toimprove the degree of freedom of the layout of the beam splitter unit.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall having optical transparency, the beamsplitter unit may be supported by the wall, and the airtight space maybe formed by the base, the support body, and the wall. Accordingly,since the base and the support body function as a part of the packageforming the airtight space, it is possible to suppress an increase inthe size of the entire module as compared with, for example, a case inwhich the package accommodating the base and the support body isprovided separately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall provided with at least one openingthrough which the first optical path and the second optical path pass,the beam splitter unit may be supported by the wall while blocking theat least one opening, and the airtight space may be formed by the base,the support body, the wall, and the beam splitter unit. Accordingly,since the base and the support body function as a part of the packageforming the airtight space, it is possible to suppress an increase inthe size of the entire module as compared with, for example, a case inwhich the package accommodating the base and the support body isprovided separately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall having optical transparency and asupport structure supporting the beam splitter unit, the beam splitterunit may be supported by the support structure while being separatedfrom the wall, and the airtight space may be formed by the base, thesupport body, and the wall. Accordingly, since the base and the supportbody function as a part of the package forming the airtight space, it ispossible to suppress an increase in the size of the entire module ascompared with, for example, a case in which the package accommodatingthe base and the support body is provided separately. Further, since themirror unit includes the support structure supporting the beam splitterunit separately from the wall having optical transparency, it ispossible to improve the degree of freedom of the layout of the beamsplitter unit.

In the optical module of an aspect of the present disclosure, in themirror unit, the mirror surface of the movable mirror and the mirrorsurface of the first fixed mirror may be disposed along the same planeparallel to the main surface, and the beam splitter unit may correct anoptical path difference between a first optical path between the beamsplitter unit and the movable mirror and a second optical path betweenthe beam splitter unit and the first fixed mirror. Accordingly, it ispossible to suppress the height of the mirror unit in the firstdirection as compared with, for example, a case in which the lighttransmitting member correcting the optical path difference is providedseparately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, and the drive unit, the packagemay include a wall having optical transparency, the beam splitter unitmay be supported by the wall, and the airtight space may be formed bythe package. Accordingly, both of the formation of the airtight spaceand the support of the beam splitter unit can be realized by the simplepackage including the wall having optical transparency.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, and the drive unit, the packagemay include a wall provided with at least one opening through which thefirst optical path and the second optical path pass, the beam splitterunit may be supported by the wall while blocking the at least oneopening, and the airtight space may be formed by the package and thebeam splitter unit. Accordingly, both of the formation of the airtightspace and the support of the beam splitter unit can be realized by thesimple package including the wall provided with at least one opening.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a package which accommodates the base, themovable mirror, the first fixed mirror, and the drive unit, the packagemay include a wall having optical transparency and a support structuresupporting the beam splitter unit, the beam splitter unit may besupported by the support structure while being separated from the wall,and the airtight space may be formed by the package. Accordingly, sincethe package includes the support structure supporting the beam splitterunit separately from the wall having optical transparency, it ispossible to improve the degree of freedom of the layout of the beamsplitter unit.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall having optical transparency, the beamsplitter unit may be supported by the wall, and the airtight space maybe formed by the base and the wall. Accordingly, since the basefunctions as a part of the package forming the airtight space, it ispossible to suppress an increase in the size of the entire module ascompared with, for example, a case in which the package accommodatingthe base is provided separately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall provided with at least one openingthrough which the first optical path and the second optical path pass,the beam splitter unit may be supported by the wall while blocking theat least one opening, and the airtight space may be formed by the base,the wall, and the beam splitter unit. Accordingly, since the basefunctions as a part of the package forming the airtight space, it ispossible to suppress an increase in the size of the entire module ascompared with, for example, a case in which the package accommodatingthe base is provided separately.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a wall having optical transparency and asupport structure supporting the beam splitter unit, the beam splitterunit may be supported by the support structure while being separatedfrom the wall, and the airtight space may be formed by the base and thewall. Accordingly, since the base functions as a part of the packageforming the airtight space, it is possible to suppress an increase inthe size of the entire module as compared with, for example, a case inwhich the package accommodating the base is provided separately.Further, since the mirror unit includes the support structure supportingthe beam splitter unit separately from the wall having opticaltransparency, it is possible to improve the degree of freedom of thelayout of the beam splitter unit.

The optical module of an aspect of the present disclosure may furtherinclude: a measurement light incident unit which is disposed so that themeasurement light is incident from the outside to the first interferenceoptical system; and a measurement light emission unit which is disposedso that the measurement light is emitted from the first interferenceoptical system to the outside. Accordingly, it is possible to obtain theFTIR including the measurement light incident unit and the measurementlight emission unit.

In the optical module of an aspect of the present disclosure, the beamsplitter unit may constitute a second interference optical system forlaser light along with the movable mirror and the first fixed mirror.Accordingly, since the interference light of the laser light isdetected, it is possible to highly accurately measure the position ofthe mirror surface of the movable mirror. Further, the beam splitterunit constitutes the first interference optical system for themeasurement light and the second interference optical system for thelaser light along with the movable mirror and the first fixed mirror.For that reason, it is possible to decrease the number of parts of themirror unit.

In the optical module of an aspect of the present disclosure, the mirrorunit may further include a second fixed mirror which includes a mirrorsurface following a plane parallel to the main surface and of which aposition with respect to the base is fixed, the beam splitter unit mayconstitute a second interference optical system for laser light alongwith the movable mirror and the second fixed mirror, the mirror surfaceof the second fixed mirror may face the one side in the first direction,and in the mirror unit, the movable mirror, the drive unit, at least apart of an optical path between the beam splitter unit and the firstfixed mirror, and at least a part of an optical path between the beamsplitter unit and the second fixed mirror may be disposed in theairtight space. Accordingly, since the interference light of the laserlight is detected, it is possible to highly accurately measure theposition of the mirror surface of the movable mirror. Further, themirror surface of the second fixed mirror faces one side in the firstdirection similarly to the mirror surface of the first fixed mirror. Forthat reason, it is possible to suppress the height of the mirror unit inthe first direction as compared with, for example, a positionalrelationship in which the mirror surface of the movable mirror and themirror surface of the second fixed mirror are orthogonal to each other.Moreover, at least a part of the optical path between the beam splitterunit and the second fixed mirror is disposed in the airtight spacesimilarly to at least a part of the optical path between the beamsplitter unit and the first fixed mirror. Accordingly, it is possible tosuppress the width of the mirror unit in a direction perpendicular tothe first direction.

The optical module of an aspect of the present disclosure may furtherinclude: a light source which generates the laser light to be incidentto the second interference optical system; and a photodetector whichdetects the laser light emitted from the second interference opticalsystem. Accordingly, since it is possible to highly accurately measurethe position of the movable mirror by detecting the laser light, it ispossible to obtain a highly accurate FTIR.

In the optical module of an aspect of the present disclosure, the base,a movable portion of the movable mirror, and the drive unit may beconfigured by an SOI substrate. Accordingly, a configuration forreliably moving the movable mirror can be appropriately realized by theSOI substrate.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide anoptical module capable of suppressing deterioration in the movableperformance of the movable mirror and an increase in the size of theentire module while enlarging the mirror surface of the movable mirror.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view of an optical module of a firstembodiment.

FIG. 2 is a longitudinal sectional view of an optical device included inthe optical module illustrated in FIG. 1 .

FIG. 3 is a plan view of the optical device illustrated in FIG. 2 .

FIG. 4 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 1 .

FIG. 5 is a longitudinal sectional view of an optical module of a secondembodiment.

FIG. 6 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 5 .

FIG. 7 is a longitudinal sectional view of an optical module of a thirdembodiment.

FIG. 8 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 7 .

FIG. 9 is a longitudinal sectional view of an optical module of a fourthembodiment.

FIG. 10 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 9 .

FIG. 11 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 9 .

FIG. 12 is a longitudinal sectional view of an optical module of a fifthembodiment.

FIG. 13 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 12 .

FIG. 14 is a longitudinal sectional view of an optical module of a sixthembodiment.

FIG. 15 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 14 .

FIG. 16 is a longitudinal sectional view of an optical module of aseventh embodiment.

FIG. 17 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 16 .

FIG. 18 is a longitudinal sectional view of an optical module of aneighth embodiment.

FIG. 19 is a longitudinal sectional view of a modified example of theoptical module illustrated in FIG. 18 .

FIG. 20 is a plan view of the optical device illustrated in FIGS. 7 to11 .

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the drawings. Furthermore, in the drawings, thesame reference numerals will be given to the same or corresponding partsand a redundant description thereof will be omitted.

First Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 1 , an optical module 1A includes a mirror unit 2and a beam splitter unit 3. The mirror unit 2 includes an optical device10 and a fixed mirror (a first fixed mirror) 21. The optical device 10includes a movable mirror 11. In the optical module 1A, the beamsplitter unit 3, the movable mirror 11, and the fixed mirror 21constitute an interference optical system (a first interference opticalsystem) I1 for measurement light L0. Here, the interference opticalsystem I1 is a Michelson interference optical system.

The optical device 10 includes a base 12, a drive unit 13, a firstoptical function portion 17, and a second optical function portion 18 inaddition to the movable mirror 11. The base 12 includes a main surface12 a. The movable mirror 11 includes a mirror surface 11 a following aplane parallel to the main surface 12 a. The movable mirror 11 issupported by the base 12 so as to be movable along a Z-axis directionperpendicular to the main surface 12 a (a direction parallel to the Zaxis, a first direction). The drive unit 13 moves the movable mirror 11along the Z-axis direction. The first optical function portion 17 isdisposed at one side of the movable mirror 11 in an X-axis directionperpendicular to the Z-axis direction (a direction parallel to the Xaxis, a second direction) when viewed from the Z-axis direction. Thesecond optical function portion 18 is disposed at the other side of themovable mirror 11 in the X-axis direction when viewed from the Z-axisdirection. The first optical function portion 17 and the second opticalfunction portion 18 are respectively light passage opening portionsprovided in the base 12 and are opened to one side and the other side inthe Z-axis direction.

The fixed mirror 21 includes a mirror surface 21 a following a planeparallel to the main surface 12 a. The position of the fixed mirror 21with respect to the base 12 is fixed. In the mirror unit 2, the mirrorsurface 11 a of the movable mirror 11 and the mirror surface 21 a of thefixed mirror 21 face one side in the Z-axis direction (the side of thebeam splitter unit 3).

The mirror unit 2 includes a support body 22, a sub-mount 23, and apackage 24 in addition to the optical device 10 and the fixed mirror 21.The package 24 accommodates the optical device 10 (the movable mirror11, the base 12, and the drive unit 13), the fixed mirror 21, thesupport body 22, and the sub-mount 23. The package 24 includes a bottomwall 241, a side wall 242, and a ceiling wall (wall) 243. The package 24is formed in, for example, a rectangular parallelepiped box shape. Thepackage 24 has, for example, a size of about 30×25×10 (thickness) mm.The bottom wall 241 and the side wall 242 are integrally formed witheach other. The ceiling wall 243 faces the bottom wall 241 in the Z-axisdirection and is air-tightly fixed to the side wall 242. The ceilingwall 243 has optical transparency with respect to the measurement lightL0. In the mirror unit 2, an airtight space S is formed by the package24. The airtight space S is, for example, an airtight space in which ahigh degree of vacuum is maintained or an airtight space filled with aninert gas such as nitrogen.

The support body 22 is fixed to the inner surface of the bottom wall 241through the sub-mount 23. The support body 22 is formed in, for example,a rectangular plate shape. The support body 22 has optical transparencywith respect to the measurement light L0. The base 12 of the opticaldevice 10 is fixed to a surface 22 a at the side opposite to thesub-mount 23 in the support body 22. That is, the base 12 is supportedby the support body 22. A concave portion 22 b is formed on the surface22 a of the support body 22 and a gap (a part of the airtight space S)is formed between the optical device 10 and the ceiling wall 243.Accordingly, the contact of the movable mirror 11 and the drive unit 13with respect to the support body 22 and the ceiling wall 243 isprevented when the movable mirror 11 is moved along the Z-axisdirection.

An opening 23 a is formed in the sub-mount 23. The fixed mirror 21 isdisposed on a surface 22 c at the side of the sub-mount 23 in thesupport body 22 so as to be located within the opening 23 a. That is,the fixed mirror 21 is disposed on the surface 22 c at the side oppositeto the base 12 in the support body 22. The fixed mirror 21 is disposedat one side of the movable mirror 11 in the X-axis direction when viewedfrom the Z-axis direction. The fixed mirror 21 overlaps the firstoptical function portion 17 of the optical device 10 when viewed fromthe Z-axis direction.

The mirror unit 2 further includes a plurality of lead pins 25 and aplurality of wires 26. Each lead pin 25 is air-tightly fixed to thebottom wall 241 while penetrating the bottom wall 241. Each lead pin 25is electrically connected to the drive unit 13 through a wire 26. In themirror unit 2, an electric signal for moving the movable mirror 11 alongthe Z-axis direction is applied to the drive unit 13 through theplurality of lead pins 25 and the plurality of wires 26.

The beam splitter unit 3 is supported by the ceiling wall 243 of thepackage 24. Specifically, the beam splitter unit 3 is fixed to a surface243 a at the side opposite to the optical device 10 in the ceiling wall243 by an optical resin 4. The optical resin 4 has optical transparencywith respect to the measurement light L0.

The beam splitter unit 3 includes a half mirror surface 31, a totalreflection mirror surface 32, and a plurality of optical surface 33 a,33 b, 33 c, and 33 d. The beam splitter unit 3 is configured by bondinga plurality of optical blocks. The half mirror surface 31 is formed by,for example, a dielectric multilayer. The total reflection mirrorsurface 32 is formed by, for example, a metal film.

The optical surface 33 a is, for example, a surface perpendicular to theZ-axis direction and overlaps the first optical function portion 17 ofthe optical device 10 and the mirror surface 21 a of the fixed mirror 21when viewed from the Z-axis direction. The measurement light L0 which isincident along the Z-axis direction is transmitted through the opticalsurface 33 a.

The half mirror surface 31 is, for example, a surface inclined by 45°with respect to the optical surface 33 a and overlaps the first opticalfunction portion 17 of the optical device 10 and the mirror surface 21 aof the fixed mirror 21 when viewed from the Z-axis direction. The halfmirror surface 31 reflects a part of the measurement light L0, which isincident to the optical surface 33 a along the Z-axis direction, alongthe X-axis direction and transmits the remaining part of the measurementlight L0 toward the fixed mirror 21 along the Z-axis direction.

The total reflection mirror surface 32 is a surface parallel to the halfmirror surface 31, overlaps the mirror surface 11 a of the movablemirror 11 when viewed from the Z-axis direction, and overlaps the halfmirror surface 31 when viewed from the X-axis direction. The totalreflection mirror surface 32 reflects a part of the measurement light L0reflected by the half mirror surface 31 toward the movable mirror 11along the Z-axis direction.

The optical surface 33 b is a surface parallel to the optical surface 33a and overlaps the mirror surface 11 a of the movable mirror 11 whenviewed from the Z-axis direction. The optical surface 33 b transmits apart of the measurement light L0 reflected by the total reflectionmirror surface 32 toward the movable mirror 11 along the Z-axisdirection.

The optical surface 33 c is a surface parallel to the optical surface 33a and overlaps the mirror surface 21 a of the fixed mirror 21 whenviewed from the Z-axis direction. The optical surface 33 c transmits theremaining part of the measurement light L0 transmitted through the halfmirror surface 31 toward the fixed mirror 21 along the Z-axis direction.

The optical surface 33 d is, for example, a surface perpendicular to theX-axis direction and overlaps the half mirror surface 31 and the totalreflection mirror surface 32 when viewed from the X-axis direction. Theoptical surface 33 d transmits the measurement light L1 along the X-axisdirection. The measurement light L1 is the interference light of a partof the measurement light L0 sequentially reflected by the mirror surface11 a of the movable mirror 11 and the total reflection mirror surface 32and transmitted through the half mirror surface 31 and the remainingpart of the measurement light L0 sequentially reflected by the mirrorsurface 21 a of the fixed mirror 21 and the half mirror surface 31.

In the optical module 1A with the above-described configuration, whenthe measurement light L0 is incident from the outside of the opticalmodule 1A to the beam splitter unit 3 through the optical surface 33 a,a part of the measurement light L0 is sequentially reflected by the halfmirror surface 31 and the total reflection mirror surface 32 and travelstoward the mirror surface 11 a of the movable mirror 11. Then, a part ofthe measurement light L0 is reflected by the mirror surface 11 a of themovable mirror 11, travels in the reverse direction on the same opticalpath (an optical path P1 to be described later), and is transmittedthrough the half mirror surface 31 of the beam splitter unit 3.

Meanwhile, the remaining part of the measurement light L0 is transmittedthrough the half mirror surface 31 of the beam splitter unit 3, passesthrough the first optical function portion 17, is further transmittedthrough the support body 22, and travels toward the mirror surface 21 aof the fixed mirror 21. Then, the remaining part of the measurementlight L0 is reflected by the mirror surface 21 a of the fixed mirror 21,travels in the reverse direction on the same optical path (an opticalpath P2 to be described later), and is reflected by the half mirrorsurface 31 of the beam splitter unit 3.

A part of the measurement light L0 transmitted through the half mirrorsurface 31 of the beam splitter unit 3 and the remaining part of themeasurement light L0 reflected by the half mirror surface 31 of the beamsplitter unit 3 become the measurement light L1 that is the interferencelight and the measurement light L1 is emitted from the beam splitterunit 3 to the outside of the optical module 1A through the opticalsurface 33 d. According to the optical module 1A, since it is possibleto reciprocate the movable mirror 11 at a high speed along the Z-axisdirection, a small and highly accurate FTIR can be provided.

The support body 22 corrects an optical path difference between anoptical path (a first optical path) P1 between the beam splitter unit 3and the movable mirror 11 and an optical path (a second optical path) P2between the beam splitter unit 3 and the fixed mirror 21. Specifically,the optical path P1 is an optical path extending from the half mirrorsurface 31 to the mirror surface 11 a of the movable mirror 11 locatedat the reference position through the total reflection mirror surface 32and the optical surface 33 b in a sequential order and is an opticalpath along which a part of the measurement light L0 travels. The opticalpath P2 is an optical path extending from the half mirror surface 31 tothe mirror surface 21 a of the fixed mirror 21 through the opticalsurface 33 c and the first optical function portion 17 in a sequentialorder and is an optical path along which the remaining part of themeasurement light L0 travels. The support body 22 corrects the opticalpath difference between the optical path P1 and the optical path P2 sothat a difference between the optical path length of the optical path P1(the optical path length considering the refractive index of each mediumthrough which the optical path P1 passes) and the optical path length ofthe optical path P2 (the optical path length considering the refractiveindex of each medium through which the optical path P2 passes)decreases. The support body 22 can be formed of, for example, a materialhaving the same optical transparency as that of each of the opticalblocks constituting the beam splitter unit 3. In this case, thethickness (the length in the Z-axis direction) of the support body 22can be the same as the distance between the half mirror surface 31 andthe total reflection mirror surface 32 in the X-axis direction.Furthermore, in the mirror unit 2, the movable mirror 11, the drive unit13, a part of the optical path P1, and a part of the optical path P2 aredisposed in the airtight space S.

[Configuration of Optical Device]

As illustrated in FIGS. 2 and 3 , the base 12, the movable portion ofthe movable mirror 11, the drive unit 13, the first optical functionportion 17, and the second optical function portion 18 are configured byan SOI substrate 50. That is, the optical device 10 is formed by the SOIsubstrate 50. The optical device 10 is formed in, for example, arectangular plate shape. The optical device 10 has, for example, a sizeof about 15×10×0.3 (thickness) mm. The SOI substrate 50 includes asupport layer 51, a device layer 52, and an intermediate layer 53.Specifically, the support layer 51 is a first silicon layer of the SOIsubstrate 50. The device layer 52 is a second silicon layer of the SOIsubstrate 50. The intermediate layer 53 is an insulation layer of theSOI substrate 50 and is disposed between the support layer 51 and thedevice layer 52. The movable mirror 11 and the drive unit 13 areintegrally formed in a part of the device layer 52 by an MEMS technology(patterning and etching).

The base 12 is formed by the support layer 51, the device layer 52, andthe intermediate layer 53. The main surface 12 a of the base 12 is asurface at the side opposite to the intermediate layer 53 in the devicelayer 52. A main surface 12 b facing the main surface 12 a in the base12 is a surface at the side opposite to the intermediate layer 53 in thesupport layer 51. In the optical module 1A, the main surface 12 a of thebase 12 is bonded to the surface 22 a of the support body 22 (see FIG. 1).

The movable mirror 11 includes a main body 111 and a wall portion 112that are movable portions. The main body 111 is formed by the devicelayer 52. The mirror surface 11 a is provided in a surface 111 a at theside of the main surface 12 b in the main body 111 by forming a metalfilm. The wall portion 112 is formed by the support layer 51 and theintermediate layer 53. The wall portion 112 is provided in the surface111 a of the main body 111. The wall portion 112 surrounds the mirrorsurface 11 a when viewed from the Z-axis direction. As an example, thewall portion 112 is provided in the surface 111 a of the main body 111so as to follow the outer edge inside the outer edge of the main body111 when viewed from the Z-axis direction and to follow the outer edgeat the outside of the outer edge of the mirror surface 11 a when viewedfrom the Z-axis direction.

The movable mirror 11 further includes a pair of brackets 113 and a pairof brackets 114 that are movable portions. The pair of brackets 113 andthe pair of brackets 114 are formed by the device layer 52. The pair ofbrackets 113 is provided in a region at the side of the first opticalfunction portion 17 in the side surface of the main body 111 so as toprotrude toward the first optical function portion 17. Each bracket 113is bent in a crank shape to the same side when viewed from the Z-axisdirection. The pair of brackets 114 is provided in a region at the sideof the second optical function portion 18 in the side surface of themain body 111 so as to protrude toward the second optical functionportion 18 (the side opposite to the first optical function portion 17).Each bracket 114 is bent in a crank shape to the same side (here, theside opposite to each bracket 113) when viewed from the Z-axisdirection.

The drive unit 13 includes a first elastic support portion 14, a secondelastic support portion 15, and an actuator 16. The first elasticsupport portion 14, the second elastic support portion 15, and theactuator 16 are formed by the device layer 52.

The first elastic support portion 14 and the second elastic supportportion 15 are connected to the base 12 and the movable mirror 11. Thefirst elastic support portion 14 and the second elastic support portion15 support the movable mirror 11 so as to be movable along the Z-axisdirection.

The first elastic support portion 14 includes a pair of first levers141, a pair of second levers 142, a plurality of torsion bars 143, 144,and 145, a plurality of links 146 and 147, and a pair of brackets 148.The pair of first levers 141 extends along the main surface 12 a of thebase 12 from the movable mirror 11 toward both sides of the firstoptical function portion 17 in a Y-axis direction perpendicular to theZ-axis direction and the X-axis direction (a direction parallel to the Yaxis, a third direction). In this embodiment, the pair of first levers141 extends along the main surface 12 a of the base 12 from a gapbetween the movable mirror 11 and the first optical function portion 17toward both sides of the first optical function portion 17 in the Y-axisdirection. The pair of first levers 141 extends along the edge of thefirst optical function portion 17 when viewed from the Z-axis direction.The pair of second levers 142 extends along the main surface 12 a of thebase 12 from both sides of the first optical function portion 17 in theY-axis direction toward the movable mirror 11. The pair of second levers142 extends along the X-axis direction outside the pair of first levers141 when viewed from the Z-axis direction.

The link 146 is laid between end portions 141 a at the side of themovable mirror 11 in the first levers 141. The link 147 is laid betweenend portions 142 a at the side opposite to the movable mirror 11 in thesecond levers 142. Each of the links 146 and 147 extends along the edgeof the first optical function portion 17 when viewed from the Z-axisdirection. The pair of brackets 148 is provided in a side surface at theside of the movable mirror 11 in the link 146 so as to protrude towardthe movable mirror 11. Each bracket 148 is bent in a crank shape to thesame side (here, the side opposite to each bracket 113) when viewed fromthe Z-axis direction. The front end portion of one bracket 148 faces thefront end portion of one bracket 113 in the Y-axis direction. The frontend portion of the other bracket 148 faces the front end portion of theother bracket 113 in the Y-axis direction.

The torsion bar 143 is laid between the front end portion of one bracket148 and the front end portion of one bracket 113 and between the frontend portion of the other bracket 148 and the front end portion of theother bracket 113. The torsion bar 143 is laid between the bracket 148and the bracket 113 which are bent in a crank shape to the oppositeside. That is, the end portion 141 a of each first lever 141 isconnected to the movable mirror 11 through the pair of torsion bars 143.The pair of torsion bars 143 is disposed on the same axis parallel tothe Y-axis direction.

The torsion bar 144 is laid between the end portion 142 a of one secondlever 142 and an end portion 141 b at the side opposite to the movablemirror 11 in one first lever 141 and between the end portion 142 a ofthe other second lever 142 and the end portion 141 b at the sideopposite to the movable mirror 11 in the other first lever 141. That is,the end portion 141 b of each first lever 141 is connected to the endportion 142 a of each second lever 142 through the pair of torsion bars144. The pair of torsion bars 144 is disposed on the same axis parallelto the Y-axis direction.

The torsion bar 145 is laid between the base 12 and an end portion 142 bat the side of the movable mirror 11 in one second lever 142 and betweenthe base 12 and the end portion 142 b at the side of the movable mirror11 in the other second lever 142. That is, the end portion 142 b of eachsecond lever 142 is connected to the base 12 through the pair of torsionbars 145. The pair of torsion bars 145 is disposed on the same axisparallel to the Y-axis direction.

The second elastic support portion 15 includes a pair of third levers151, a pair of fourth levers 152, a plurality of torsion bars 153, 154,and 155, a plurality of links 156 and 157, and a pair of brackets 158.The pair of third levers 151 extends along the main surface 12 a of thebase 12 from the movable mirror 11 toward both sides of the secondoptical function portion 18 in the Y-axis direction. In this embodiment,the pair of third levers 151 extends from a gap between the movablemirror 11 and the second optical function portion 18 toward both sidesof the second optical function portion 18 in the Y-axis direction. Thepair of third levers 151 extends along the edge of the second opticalfunction portion 18 when viewed from the Z-axis direction. The pair offourth levers 152 extends along the main surface 12 a of the base 12from both sides of the second optical function portion 18 in the Y-axisdirection toward the movable mirror 11. The pair of fourth levers 152extends along the X-axis direction outside the pair of third levers 151when viewed from the Z-axis direction.

The link 156 is laid between end portions 151 a at the side of themovable mirror 11 in the third levers 151. The link 157 is laid betweenend portions 152 a at the side opposite to the movable mirror 11 in thefourth levers 152. Each of the links 156 and 157 extends along the edgeof the second optical function portion 18 when viewed from the Z-axisdirection. The pair of brackets 158 is provided in a side surface at theside of the movable mirror 11 in the link 156 so as to protrude towardthe movable mirror 11. Each bracket 158 is bent in a crank shape to thesame side (here, the side opposite to each bracket 114) when viewed fromthe Z-axis direction. The front end portion of one bracket 158 faces thefront end portion of one bracket 114 in the Y-axis direction. The frontend portion of the other bracket 158 faces the front end portion of theother bracket 114 in the Y-axis direction.

The torsion bar 153 is laid between the front end portion of one bracket158 and the front end portion of one bracket 114 and between the frontend portion of the other bracket 158 and the front end portion of theother bracket 114. The torsion bar 153 is laid between the bracket 158and the bracket 114 which are bent in a crank shape to the oppositeside. That is, the end portions 151 a of the third levers 151 areconnected to the movable mirror 11 through the pair of torsion bars 153.The pair of torsion bars 153 is disposed on the same axis parallel tothe Y-axis direction.

The torsion bar 154 is laid between the end portion 152 a of one fourthlever 152 and an end portion 151 b at the side opposite to the movablemirror 11 in one third lever 151 and between the end portion 152 a ofthe other fourth lever 152 and the end portion 151 b at the sideopposite to the movable mirror 11 in the other third lever 151. That is,the end portion 151 b of each third lever 151 is connected to the endportion 152 a of each fourth lever 152 through the pair of torsion bars154. The pair of torsion bars 154 is disposed on the same axis parallelto the Y-axis direction.

The torsion bar 155 is laid between the base 12 and an end portion 152 bat the side of the movable mirror 11 in one fourth lever 152 and betweenthe base 12 and the end portion 152 b at the side of the movable mirror11 in the other fourth lever 152. That is, the end portion 152 b of eachfourth lever 152 is connected to the base 12 through the pair of torsionbars 155. The pair of torsion bars 155 is disposed on the same axisparallel to the Y-axis direction.

The first optical function portion 17 is defined by at least the pair offirst levers 141 and the plurality of links 146 and 147. In the firstelastic support portion 14, a length A1 of each first lever 141 in theX-axis direction is larger than the shortest distance D1 between theouter edge of the mirror surface 11 a and the edge of the first opticalfunction portion 17 (the shortest distance when viewed from the Z-axisdirection). A maximum distance D2 between the pair of first levers 141in the Y-axis direction is the same as a maximum width W1 of the firstoptical function portion 17 in the Y-axis direction (the maximum widthwhen viewed from the Z-axis direction). A distance D3 from a portionclosest to the mirror surface 11 a in the edge of the first opticalfunction portion 17 to the end portion 141 b of each first lever 141(the distance when viewed from the Z-axis direction) is larger than adistance D4 from a portion farthest from the mirror surface 11 a in theedge of the first optical function portion 17 to the end portion 141 bof each first lever 141 (the distance when viewed from the Z-axisdirection).

The second optical function portion 18 is defined by at least the pairof third levers 151 and the plurality of links 156 and 157. In thesecond elastic support portion 15, a length A2 of each third lever 151in the X-axis direction is larger than the shortest distance D5 betweenthe outer edge of the mirror surface 11 a and the edge of the secondoptical function portion 18 (the shortest distance when viewed from theZ-axis direction). A maximum distance D6 between the pair of thirdlevers 151 in the Y-axis direction is the same as a maximum width W2 ofthe second optical function portion 18 in the Y-axis direction (themaximum width when viewed from the Z-axis direction). A distance D7 froma portion closest to the mirror surface 11 a in the edge of the secondoptical function portion 18 to the end portion 151 b of each third lever151 (the distance when viewed from the Z-axis direction) is larger thana distance D8 from a portion farthest from the mirror surface 11 a inthe edge of the second optical function portion 18 to the end portion151 b of each third lever 151 (the distance when viewed from the Z-axisdirection).

The first elastic support portion 14 and the second elastic supportportion 15 do not have a symmetrical structure with respect to a planepassing through the center of the movable mirror 11 and perpendicular tothe X-axis direction and a plane passing through the center of themovable mirror 11 and perpendicular to the Y-axis direction. Here, aportion excluding the pair of brackets 148 in the first elastic supportportion 14 and a portion excluding the pair of brackets 158 in thesecond elastic support portion 15 have a symmetrical structure withrespect to a plane passing through the center of the movable mirror 11and perpendicular to the X-axis direction and a plane passing throughthe center of the movable mirror 11 and perpendicular to the Y-axisdirection.

The actuator 16 moves the movable mirror 11 along the Z-axis direction.The actuator 16 includes a pair of comb electrodes 161 and a pair ofcomb electrodes 162 disposed along the outer edge of the movable mirror11. One comb electrode 161 is provided in a region 111 b between onebracket 113 and one bracket 114 in the side surface of the main body 111of the movable mirror 11. The other comb electrode 161 is provided in aregion 111 c between the other bracket 113 and the other bracket 114 inthe side surface of the main body 111 of the movable mirror 11. One combelectrode 162 is provided in a region extending along the region 111 bwhile being separated from the region 111 b of the main body 111 in theside surface of the device layer 52 of the base 12. The other combelectrode 162 is provided in a region extending along the region 111 cwhile being separated from the region 111 c of the main body 111 in theside surface of the device layer 52 of the base 12. In one combelectrode 161 and one comb electrode 162, each comb finger of one combelectrode 161 is located between respective comb fingers of one combelectrode 162. In the other comb electrode 161 and the other combelectrode 162, each comb finger of the other comb electrode 161 islocated between respective comb fingers of the other comb electrode 162.

The base 12 is provided with a plurality of electrode pads 121 and 122.Each of the electrode pads 121 and 122 is formed on the surface of thedevice layer 52 inside an opening 12 c formed in the main surface 12 bof the base 12 so as to reach the device layer 52. Each electrode pad121 is electrically connected to the comb electrode 161 through thefirst elastic support portion 14 and the main body 111 of the movablemirror 11 or the second elastic support portion 15 and the main body 111of the movable mirror 11. Each electrode pad 122 is electricallyconnected to the comb electrode 162 through the device layer 52. Thewire 26 is laid between each of the electrode pads 121 and 122 and eachlead pin 25.

In the optical device 10 with the above-described configuration, when avoltage is applied across the plurality of electrode pads 121 and theplurality of electrode pads 122 through the plurality of lead pins 25and the plurality of wires 26, for example, an electrostatic force isgenerated between the comb electrode 161 and the comb electrode 162facing each other so that the movable mirror 11 is moved to one side inthe Z-axis direction. At this time, the torsion bars 143, 144, 145, 153,154, and 155 are twisted in the first elastic support portion 14 and thesecond elastic support portion 15 so that an elastic force is generatedin the first elastic support portion 14 and the second elastic supportportion 15. In the optical device 10, when a periodic electrical signalis applied to the drive unit 13 through the plurality of lead pins 25and the plurality of wires 26, the movable mirror 11 can be reciprocatedalong the Z-axis direction at the resonance frequency level. In thisway, the drive unit 13 functions as an electrostatic actuator.

[Operation and Effect]

In the optical module 1A, the movable mirror 11 includes the mirrorsurface 11 a following a plane parallel to the main surface 12 a of thebase 12. Accordingly, the mirror surface 11 a of the movable mirror 11can be enlarged. Further, in the mirror unit 2, the movable mirror 11and the drive unit 13 are disposed in the airtight space S. Accordingly,since the drive unit 13 moving the movable mirror 11 is hardlyinfluenced by the external environment, deterioration in the movableperformance of the movable mirror 11 can be suppressed. Moreover, themirror surface 11 a of the movable mirror 11 and the mirror surface 21 aof the fixed mirror 21 face one side in the Z-axis directionperpendicular to the main surface 12 a. Accordingly, the height of themirror unit 2 in the Z-axis direction can be suppressed as comparedwith, for example, a positional relationship in which the mirror surface11 a of the movable mirror 11 and the mirror surface 21 a of the fixedmirror 21 are orthogonal to each other. Moreover, a part of the opticalpath P2 between the beam splitter unit 3 and the fixed mirror 21 isdisposed in the airtight space S in addition to a part of the opticalpath P1 between the beam splitter unit 3 and the movable mirror 11.Accordingly, it is possible to suppress the width of the mirror unit 2in a direction (in the optical module 1A, the X-axis direction)perpendicular to the Z-axis direction. As described above, according tothe optical module 1A, it is possible to suppress deterioration in themovable performance of the movable mirror 11 and an increase in the sizeof the entire module while enlarging the mirror surface 11 a of themovable mirror 11.

In the optical module 1A, the support body 22 which supports the base 12of the optical device 10 and in which the fixed mirror 21 is disposed onthe surface 22 c corrects the optical path difference between theoptical path P1 between the beam splitter unit 3 and the movable mirror11 and the optical path P2 between the beam splitter unit 3 and thefixed mirror 21. Accordingly, the interference light (that is, themeasurement light L1) of the measurement light L0 can be easily andhighly accurately obtained. Moreover, a light transmitting membercorrecting the optical path difference does not need to be providedseparately.

In the optical module 1A, the package 24 includes the ceiling wall 243having optical transparency, the beam splitter unit 3 is supported bythe ceiling wall 243 of the package 24, and the airtight space S isformed by the package 24. Accordingly, both of the formation of theairtight space S and the support of the beam splitter unit 3 can berealized by the simple package 24 including the ceiling wall 243 havingoptical transparency.

In the optical module 1A, the base 12, the main body 111 of the movablemirror 11, the wall portion 112, the plurality of brackets 113 and 114,and the drive unit 13 are configured by the SOI substrate 50.Accordingly, a configuration for reliably moving the movable mirror 11can be appropriately realized by the SOI substrate 50.

In the optical device 10, the first elastic support portion 14 includesthe pair of first levers 141 extending along the main surface 12 a fromthe movable mirror 11 toward both sides of the first optical functionportion 17 and the length of each first lever 141 in the X-axisdirection where the movable mirror 11 and the first optical functionportion 17 are arranged is larger than the shortest distance between theouter edge of the mirror surface 11 a and the edge of the first opticalfunction portion 17. Accordingly, since an increase in the distancebetween the movable mirror 11 and the first optical function portion 17is suppressed, it is possible to suppress an increase in the size of theentire device. Further, since the length of each first lever 141 of thefirst elastic support portion 14 is secured, it is possible to suppressdeterioration in the movable performance of the movable mirror 11. Asdescribed above, according to the optical device 10, it is possible tosuppress deterioration in the movable performance of the movable mirror11 and an increase in the size of the entire device while enlarging themirror surface 11 a of the movable mirror 11.

In the optical device 10, the maximum distance between the pair of firstlevers 141 in the Y-axis direction is the same as the maximum width ofthe first optical function portion 17 in the Y-axis direction.Accordingly, it is possible to realize the suppressing of an increase inthe distance between the movable mirror 11 and the first opticalfunction portion 17 and the securing of the length of each first lever141 with higher balance.

In the optical device 10, the distance from a portion closest to themirror surface 11 a in the edge of the first optical function portion 17to the end portion 141 b at the side opposite to the movable mirror 11in each first lever 141 is larger than the distance from a portionfarthest from the mirror surface 11 a in the edge of the first opticalfunction portion 17 to the end portion 141 b at the side opposite to themovable mirror 11 in each first lever 141. Accordingly, it is possibleto realize the suppressing of an increase in the distance between themovable mirror 11 and the first optical function portion 17 and thesecuring of the length of each first lever 141 with higher balance.

In the optical device 10, the first elastic support portion 14 furtherincludes the pair of second levers 142 extending along the main surface12 a from both sides of the first optical function portion 17 in theY-axis direction toward the movable mirror 11 and the connection of thepair of first levers 141, the pair of second levers 142, and the base 12is realized through the plurality of torsion bars 143, 144, and 145.Similarly, the second elastic support portion 15 includes the pair offourth levers 152 in addition to the pair of third levers 151 and theconnection of the pair of third levers 151, the pair of fourth levers152, and the base 12 is realized through the plurality of torsion bars153, 154, and 155. Accordingly, it is possible to increase the movablerange of the movable mirror 11 and to improve the movable efficiency ofthe movable mirror 11 (to reduce the driving force necessary for drivingthe movable mirror 11).

In the optical device 10, the end portion 141 a at the side of themovable mirror 11 in each first lever 141 is connected to the movablemirror 11 through the plurality of torsion bars 143 disposed on the sameaxis parallel to the Y-axis direction. Similarly, the end portion 151 aat the side of the movable mirror 11 in each third lever 151 isconnected to the movable mirror 11 through the plurality of torsion bars153 disposed on the same axis parallel to the Y-axis direction.Accordingly, it is possible to shorten the length of each torsion bar143 disposed on the same axis. Similarly, it is possible to shorten thelength of each torsion bar 153 disposed on the same axis. As a result,it is possible to suppress the movement of the movable mirror 11 in theX-axis direction and the rotation of the movable mirror 11 around theaxis parallel to the Z-axis direction.

In the first elastic support portion 14 of the optical device 10, thelink 146 is laid between the end portions 141 a at the side of themovable mirror 11 in the first levers 141 and the link 147 is laidbetween the end portions 142 a at the side opposite to the movablemirror 11 in the second levers 142. Similarly, in the second elasticsupport portion 15, the link 156 is laid between the end portions 151 aat the side of the movable mirror 11 in the third levers 151 and thelink 157 is laid between the end portions 152 a at the side opposite tothe movable mirror 11 in the fourth levers 152. Accordingly, thestability of movement of the movable mirror 11 can be improved. Further,each of the links 146 and 147 extends along the edge of the firstoptical function portion 17 when viewed from the Z-axis direction.Accordingly, an increase in the size of the entire device can besuppressed.

In the optical device 10, the actuator 16 includes the comb electrodes161 and 162 disposed along the outer edge of the movable mirror 11.Accordingly, the electrostatic force generated by the comb electrodes161 and 162 can be efficiently used as the driving force of the movablemirror 11.

In the optical device 10, the main body 111 of the movable mirror 11 isprovided with the wall portion 112 surrounding the mirror surface 11 awhen viewed from the Z-axis direction. Accordingly, since the wallportion 112 functions as a rib, it is possible to suppress thedeformation (warping, bending, or the like) of the mirror surface 11 awhile thinning the main body 111.

[Modified Example of First Embodiment]

As illustrated in (a) of FIG. 4 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Aillustrated in (a) of FIG. 4 , the ceiling wall 243 of the package 24 isprovided with an opening 243 b through which the optical path P1 passesand an opening 243 c through which the optical path P2 passes. Each ofthe openings 243 b and 243 c penetrates the ceiling wall 243 in theZ-axis direction. The beam splitter unit 3 is supported by the ceilingwall 243 while blocking each of the openings 243 b and 243 c.Specifically, the beam splitter unit 3 is fixed to the surface 243 a ofthe ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical path P1 passes and the opening 243 c throughwhich the optical path P2 passes. Furthermore, in the optical module 1Aillustrated in (a) of FIG. 4 , the ceiling wall 243 may not have opticaltransparency with respect to the measurement light L0. Further, when theoptical resin 4 does not enter each of the openings 243 b and 243 c, aresin that does not have optical transparency with respect to themeasurement light L0 may be used instead of the optical resin 4.Further, the ceiling wall 243 of the package 24 may be provided with oneopening through which the plurality of optical paths P1 and P2 pass.

Further, as illustrated in (b) of FIG. 4 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Aillustrated in (b) of FIG. 4 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to an inner surfaceof a concave portion 271 a by the optical resin 4 while a part of thebeam splitter unit 3 is disposed in the concave portion 271 a formed inthe wall portion 271 of the support structure 27. The wall portion 271faces the ceiling wall 243 in the Z-axis direction and the concaveportion 271 a is opened to the side opposite to the ceiling wall 243 inthe Z-axis direction. The bottom surface of the concave portion 271 a isprovided with one opening 271 b through which the plurality of opticalpaths P1 and P2 pass. According to such a configuration, since thesupport structure 27 supporting the beam splitter unit 3 is providedseparately from the package 24, the degree of freedom of the layout ofthe beam splitter unit 3 can be improved. Furthermore, when the opticalresin 4 does not enter the opening 271 b, a resin that does not haveoptical transparency with respect to the measurement light L0 may beused instead of the optical resin 4.

Second Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 5 , an optical module 1B is different from theoptical module 1A illustrated in FIG. 1 in that the airtight space S isformed by the base 12, the support body 22, and a support wall (wall)29. In the optical module 1B, the sub-mount 23 is fixed onto a substrate28 and the plurality of lead pins 25 are fixed to the substrate 28 whilepenetrating the substrate 28.

The support wall 29 is fixed to the main surface 12 b of the base 12.The support wall 29 is formed in, for example, a rectangular plateshape. The support wall 29 has optical transparency with respect to themeasurement light L0. A concave portion 29 c is formed in a surface 29 aat the side of the base 12 in the support wall 29. Accordingly, thecontact of the movable mirror 11 and the drive unit 13 with respect tothe support wall 29 when the movable mirror 11 is moved along the Z-axisdirection is prevented. The beam splitter unit 3 is supported by thesupport wall 29. Specifically, the beam splitter unit 3 is fixed to asurface 29 b at the side opposite to the optical device 10 in thesupport wall 29 by the optical resin 4. The optical resin 4 has opticaltransparency with respect to the measurement light L0.

[Operation and Effect]

According to the optical module 1B, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1B, the airtight space S is formed by the base 12,the support body 22, and the support wall 29. Accordingly, since thebase 12 and the support body 22 function as a part of the package 24forming the airtight space S, it is possible to suppress an increase inthe size of the entire module as compared with, for example, a case inwhich the package accommodating the base 12 and the support body 22 isprovided separately.

[Modified Example of Second Embodiment]

As illustrated in (a) of FIG. 6 , the airtight space S may be formed bythe base 12, the support body 22, the support wall 29, and the beamsplitter unit 3. In the optical module 1B illustrated in (a) of FIG. 6,the support wall 29 is provided with an opening 29 d through which theoptical path P1 passes and an opening 29 e through which the opticalpath P2 passes. Each of the openings 29 d and 29 e penetrates thesupport wall 29 in the Z-axis direction. The beam splitter unit 3 issupported by the support wall 29 while blocking each of the openings 29d and 29 e. Specifically, the beam splitter unit 3 is fixed to thesurface 29 b of the support wall 29 by the optical resin 4. According tosuch a configuration, since the base 12 and the support body 22 functionas a part of the package forming the airtight space S, it is possible tosuppress an increase in the size of the entire module as compared with,for example, a case in which the package accommodating the base 12 andthe support body 22 is provided separately. Furthermore, in the opticalmodule 1B illustrated in (a) of FIG. 6 , the support wall 29 may nothave optical transparency with respect to the measurement light L0.Further, when the optical resin 4 does not enter each of the openings 29d and 29 e, a resin that does not have optical transparency with respectto the measurement light L0 may be used instead of the optical resin 4.Further, the support wall 29 may be provided with one opening throughwhich the plurality of optical paths P1 and P2 pass.

Further, as illustrated in (b) of FIG. 6 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thesupport wall 29. In the optical module 1B illustrated in (b) of FIG. 6 ,the beam splitter unit 3 is supported by the support structure 27 whilebeing separated from the support wall 29. Specifically, the beamsplitter unit 3 is fixed to the inner surface of the concave portion 271a by the optical resin 4 while a part of the beam splitter unit 3 isdisposed in the concave portion 271 a formed in the wall portion 271 ofthe support structure 27. The wall portion 271 faces the support wall 29in the Z-axis direction and the concave portion 271 a is opened to theside opposite to the support wall 29 in the Z-axis direction. The bottomsurface of the concave portion 271 a is provided with one opening 271 bthrough which the plurality of optical paths P1 and P2 pass. Accordingto such a configuration, since the base 12 and the support body 22function as a part of the package forming the airtight space S, it ispossible to suppress an increase in the size of the entire module ascompared with, for example, a case in which the package accommodatingthe base 12 and the support body 22 is provided separately. Further,since the mirror unit 2 includes the support structure 27 supporting thebeam splitter unit 3 separately from the support wall 29, the degree offreedom of the layout of the beam splitter unit 3 can be improved.Furthermore, when the optical resin 4 does not enter the opening 271 b,a resin that does not have optical transparency with respect to themeasurement light L0 may be used instead of the optical resin 4.

Third Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 7 , an optical module 1C is mainly different fromthe optical module 1A illustrated in FIG. 1 in that the mirror surface11 a of the movable mirror 11 and the mirror surface 21 a of the fixedmirror 21 are disposed along the same plane parallel to the main surface12 a of the base 12 and the beam splitter unit 3 corrects the opticalpath difference between the optical path P1 and the optical path P2. Inthe optical module 1C, the base 12 of the optical device 10 is fixed tothe inner surface of the bottom wall 241 of the package 24. In theoptical module 1C, the optical device 10 is disposed so that the mainsurface 12 a of the base 12 faces the inner surface of the ceiling wall243 and the main surface 12 b of the base 12 faces the inner surface ofthe bottom wall 241.

A metal film forming the movable mirror 11 is formed on a plane of themovable mirror 11 including the main surface 12 a of the base 12. Ametal film forming the fixed mirror 21 is formed on the main surface 12a of the base 12. In this case, the fixed mirror 21 functions as thefirst optical function portion 17.

The beam splitter unit 3 includes a plurality of total reflection mirrorsurfaces 34 a and 34 b in addition to the half mirror surface 31, thetotal reflection mirror surface 32, and the plurality of opticalsurfaces 33 a, 33 b, 33 c, and 33 d. The beam splitter unit 3 isconfigured by bonding a plurality of optical blocks. Each of the totalreflection mirror surfaces 34 a and 34 b is formed by, for example, ametal film. The total reflection mirror surface 34 a is, for example, asurface inclined by 45° toward the side opposite to the half mirrorsurface 31 with respect to the optical surface 33 a and overlaps thehalf mirror surface 31 when viewed from the Z-axis direction. The totalreflection mirror surface 34 a reflects the remaining part of themeasurement light L0 transmitted through the half mirror surface 31along the X-axis direction. The total reflection mirror surface 34 b isa surface parallel to the total reflection mirror surface 34 a, overlapsthe mirror surface 21 a of the fixed mirror 21 when viewed from theZ-axis direction, and overlaps the total reflection mirror surface 34 awhen viewed from the X-axis direction. The total reflection mirrorsurface 34 b reflects the remaining part of the measurement light L0reflected by the total reflection mirror surface 34 a toward the fixedmirror 21 along the Z-axis direction.

In the optical module 1C with the above-described configuration, whenthe measurement light L0 is incident from the outside of the opticalmodule 1C to the beam splitter unit 3 through the optical surface 33 a,a part of the measurement light L0 is sequentially reflected by the halfmirror surface 31 and the total reflection mirror surface 32 and travelstoward the mirror surface 11 a of the movable mirror 11. Then, a part ofthe measurement light L0 is reflected by the mirror surface 11 a of themovable mirror 11, travels in the reverse direction on the same opticalpath (the optical path P1), and is transmitted through the half mirrorsurface 31 of the beam splitter unit 3.

Meanwhile, the remaining part of the measurement light L0 is transmittedthrough the half mirror surface 31 of the beam splitter unit 3, issequentially reflected by the plurality of total reflection mirrorsurfaces 34 a and 34 b, and travels toward the mirror surface 21 a ofthe fixed mirror 21. Then, the remaining part of the measurement lightL0 is reflected by the mirror surface 21 a of the fixed mirror 21,travels in the reverse direction on the same optical path (the opticalpath P2), and is reflected by the half mirror surface 31 of the beamsplitter unit 3.

A part of the measurement light L0 transmitted through the half mirrorsurface 31 of the beam splitter unit 3 and the remaining part of themeasurement light L0 reflected by the half mirror surface 31 of the beamsplitter unit 3 become the measurement light L1 that is the interferencelight and the measurement light L1 is emitted from the beam splitterunit 3 to the outside of the optical module 1C through the opticalsurface 33 d. In the optical module 1C, the beam splitter unit 3corrects the optical path difference between the optical path P1 betweenthe beam splitter unit 3 and the movable mirror 11 and the optical pathP2 between the beam splitter unit 3 and the fixed mirror 21.

[Operation and Effect]

According to the optical module 1C, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1C, the mirror surface 11 a of the movable mirror11 and the mirror surface 21 a of the fixed mirror 21 are disposed alongthe same plane parallel to the main surface 12 a of the base 12 and thebeam splitter unit 3 corrects the optical path difference between theoptical path P1 and the optical path P2. Accordingly, the height of themirror unit 2 in the Z-axis direction can be suppressed as comparedwith, for example, a case in which a light transmitting member forcorrecting the optical path difference is provided separately.

In the optical module 1C, the beam splitter unit 3 is supported by theceiling wall 243 of the package 24 and the airtight space S is formed bythe package 24. Accordingly, both of the formation of the airtight spaceS and the support of the beam splitter unit 3 can be realized by thesimple package 24 including the ceiling wall 243 having opticaltransparency.

[Modified Example of Third Embodiment]

As illustrated in (a) of FIG. 8 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Cillustrated in (a) of FIG. 8 , the ceiling wall 243 of the package 24 isprovided with an opening 243 b through which the optical path P1 passesand an opening 243 c through which the optical path P2 passes. Each ofthe openings 243 b and 243 c penetrates the ceiling wall 243 in theZ-axis direction. The beam splitter unit 3 is supported by the ceilingwall 243 while blocking each of the openings 243 b and 243 c.Specifically, the beam splitter unit 3 is fixed to the surface 243 a ofthe ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical path P1 passes and the opening 243 c throughwhich the optical path P2 passes. Furthermore, in the optical module 1Cillustrated in (a) of FIG. 8 , the ceiling wall 243 may not have opticaltransparency with respect to the measurement light L0. Further, when theoptical resin 4 does not enter each of the openings 243 b and 243 c, aresin that does not have optical transparency with respect to themeasurement light L0 may be used instead of the optical resin 4.Further, the ceiling wall 243 of the package 24 may be provided with oneopening through which the plurality of optical paths P1 and P2 pass.

Further, as illustrated in (b) of FIG. 8 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Cillustrated in (b) of FIG. 8 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to the innersurface of the concave portion 271 a by the optical resin 4 while a partof the beam splitter unit 3 is disposed in the concave portion 271 aformed in the wall portion 271 of the support structure 27. The wallportion 271 faces the ceiling wall 243 in the Z-axis direction and theconcave portion 271 a is opened to the side opposite to the ceiling wall243 in the Z-axis direction. The bottom surface of the concave portion271 a is provided with one opening 271 b through which the plurality ofoptical paths P1 and P2 pass. According to such a configuration, sincethe support structure 27 supporting the beam splitter unit 3 is providedseparately from the package 24, the degree of freedom of the layout ofthe beam splitter unit 3 can be improved. Furthermore, when the opticalresin 4 does not enter the opening 271 b, a resin that does not haveoptical transparency with respect to the measurement light L0 may beused instead of the optical resin 4.

Fourth Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 9 , an optical module 1D is mainly different fromthe optical module 1C illustrated in FIG. 7 in that the airtight space Sis formed by the base 12, the sub-mount 23, and the support wall (wall)29. In the optical module 1D, the sub-mount 23 is fixed onto thesubstrate 28 and the plurality of lead pins 25 is fixed to the substrate28 while penetrating the substrate 28.

The support wall 29 is fixed to the main surface 12 a of the base 12.The support wall 29 is formed in, for example, a rectangular plateshape. The support wall 29 has optical transparency with respect to themeasurement light L0. The concave portion 29 c is formed in the surface29 a at the side of the base 12 in the support wall 29. Accordingly, thecontact of the movable mirror 11 and the drive unit 13 with respect tothe support wall 29 when the movable mirror 11 is moved along the Z-axisdirection is prevented. The beam splitter unit 3 is supported by thesupport wall 29. Specifically, the beam splitter unit 3 is fixed to thesurface 29 b at the side opposite to the optical device 10 in thesupport wall 29 by the optical resin 4. The optical resin 4 has opticaltransparency with respect to the measurement light L0.

[Operation and Effect]

According to the optical module 1D, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1D, the airtight space S is formed by the base 12,the sub-mount 23, and the support wall 29. Accordingly, since the base12 functions as a part of the package 24 forming the airtight space S,it is possible to suppress an increase in the size of the entire moduleas compared with, for example, a case in which the package accommodatingthe base 12 is provided separately.

[Modified Example of Fourth Embodiment]

As illustrated in (a) of FIG. 10 , the airtight space S may be formed bythe base 12, the sub-mount 23, the support wall 29, and the beamsplitter unit 3. In the optical module 1D illustrated in (a) of FIG. 10, the support wall 29 is provided with an opening 29 d through which theoptical path P1 passes and an opening 29 e through which the opticalpath P2 passes. Each of the openings 29 d and 29 e penetrates thesupport wall 29 in the Z-axis direction. The beam splitter unit 3 issupported by the support wall 29 while blocking each of the openings 29d and 29 e. Specifically, the beam splitter unit 3 is fixed to thesurface 29 b of the support wall 29 by the optical resin 4. According tosuch a configuration, since the base 12 functions as a part of thepackage forming the airtight space S, it is possible to suppress anincrease in the size of the entire module as compared with, for example,a case in which the package accommodating the base 12 is providedseparately. Furthermore, in the optical module 1D illustrated in (a) ofFIG. 10 , the support wall 29 may not have optical transparency withrespect to the measurement light L0. Further, when the optical resin 4does not enter each of the openings 29 d and 29 e, a resin that does nothave optical transparency with respect to the measurement light L0 maybe used instead of the optical resin 4. Further, the support wall 29 maybe provided with one opening through which the plurality of opticalpaths P1 and P2 pass.

Further, as illustrated in (b) of FIG. 10 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thesupport wall 29. In the optical module 1D illustrated in (b) of FIG. 10, the beam splitter unit 3 is supported by the support structure 27while being separated from the support wall 29. Specifically, the beamsplitter unit 3 is fixed to the inner surface of the concave portion 271a by the optical resin 4 while a part of the beam splitter unit 3 isdisposed in the concave portion 271 a formed in the wall portion 271 ofthe support structure 27. The wall portion 271 faces the support wall 29in the Z-axis direction and the concave portion 271 a is opened to theside opposite to the support wall 29 in the Z-axis direction. The bottomsurface of the concave portion 271 a is provided with one opening 271 bthrough which the plurality of optical paths P1 and P2 pass. Accordingto such a configuration, since the base 12 functions as a part of thepackage forming the airtight space S, it is possible to suppress anincrease in the size of the entire module as compared with, for example,a case in which the package accommodating the base 12 is providedseparately. Further, since the mirror unit 2 includes the supportstructure 27 supporting the beam splitter unit 3 separately from thesupport wall 29, the degree of freedom of the layout of the beamsplitter unit 3 can be improved. Furthermore, when the optical resin 4does not enter the opening 271 b, a resin that does not have opticaltransparency with respect to the measurement light L0 may be usedinstead of the optical resin 4.

Further, as illustrated in FIG. 11 , in the optical module 1D, thesub-mount 23 may not be provided. In this case, since a portioncorresponding to the sub-mount 23 is integrally formed by the supportlayer 51 (see FIG. 2 ) as the base 12, the airtight space S can beeasily and reliably formed.

Fifth Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 12 , an optical module 1E is mainly differentfrom the optical module 1A illustrated in FIG. 1 in that the beamsplitter unit 3 constitutes an interference optical system I1 for themeasurement light L0 and an interference optical system (a secondinterference optical system) I2 for the laser light L10 along with themovable mirror 11 and the fixed mirror 21. The optical module 1Eincludes a light source 5, a photodetector 6, a plurality of circuitboards 7, and a half mirror 8. The light source 5 generates the laserlight L10 to be incident to the interference optical system I2. Thelight source 5 is configured as, for example, a laser diode or the like.The photodetector 6 detects the laser light L11 emitted from theinterference optical system I2 (the interference light of the laserlight L10). The photodetector 6 is configured as, for example, aphotodiode or the like. The light source 5 and the photodetector 6 aremounted on another circuit board 7. The half mirror 8 transmits thelaser light L10 emitted from the light source 5 and reflects the laserlight L11 emitted from the interference optical system I2.

The beam splitter unit 3 includes the half mirror surface 31, the totalreflection mirror surface 32, a dichroic mirror surface 35, and aplurality of optical surfaces 36 a, 36 b, 36 c, and 36 d. The beamsplitter unit 3 is configured by bonding a plurality of optical blocks.The dichroic mirror surface 35 is formed by, for example, a dielectricmultilayer.

The optical surface 36 a is, for example, a surface perpendicular to theX-axis direction. The half mirror surface 31 is, for example, a surfaceinclined by 45° with respect to the optical surface 36 a, overlaps themirror surface 21 a of the fixed mirror 21 when viewed from the Z-axisdirection, and overlaps the optical surface 36 a when viewed from theX-axis direction. The total reflection mirror surface 32 is a surfaceparallel to the half mirror surface 31, overlaps the mirror surface 11 aof the movable mirror 11 when viewed from the Z-axis direction, andoverlaps the half mirror surface 31 when viewed from the X-axisdirection.

The optical surface 36 b is a surface perpendicular to the opticalsurface 36 a and overlaps the mirror surface 11 a of the movable mirror11 when viewed from the Z-axis direction. The optical surface 36 b islocated between the total reflection mirror surface 32 and the mirrorsurface 11 a of the movable mirror 11 in the Z-axis direction. Theoptical surface 36 c is a surface perpendicular to the optical surface36 a and overlaps the mirror surface 21 a of the fixed mirror 21 whenviewed from the Z-axis direction. The optical surface 36 c is locatedbetween the half mirror surface 31 and the mirror surface 21 a of thefixed mirror 21 in the Z-axis direction. The optical surface 36 d is asurface perpendicular to the optical surface 36 a and overlaps themirror surface 21 a of the fixed mirror 21 when viewed from the Z-axisdirection. The optical surface 36 d is located at the side opposite tothe mirror surface 21 a of the fixed mirror 21 with respect to the halfmirror surface 31 in the Z-axis direction.

An optical surface 36 e is, for example, a surface perpendicular to theX-axis direction. The dichroic mirror surface 35 is, for example, asurface inclined by 45° toward the side opposite to the half mirrorsurface 31 with respect to the optical surface 36 e, overlaps the mirrorsurface 21 a of the fixed mirror 21 when viewed from the Z-axisdirection, and overlaps the optical surface 36 e when viewed from theX-axis direction. The dichroic mirror surface 35 is located between theoptical surface 36 d and the half mirror surface 31 in the Z-axisdirection.

In the optical module 1E with the above-described configuration, whenthe measurement light L0 is incident from the outside of the opticalmodule 1E to the beam splitter unit 3 through the optical surface 36 a,a part of the measurement light L0 is transmitted through the halfmirror surface 31, is reflected by the total reflection mirror surface32, and travels toward the mirror surface 11 a of the movable mirror 11.Then, a part of the measurement light L0 is reflected by the mirrorsurface 11 a of the movable mirror 11, travels in the reverse directionon the same optical path (the optical path P1), and is reflected by thehalf mirror surface 31.

Meanwhile, the remaining part of the measurement light L0 is reflectedby the half mirror surface 31, passes through the first optical functionportion 17, is further transmitted through the support body 22, andtravels toward the mirror surface 21 a of the fixed mirror 21. Then, theremaining part of the measurement light L0 is reflected by the mirrorsurface 21 a of the fixed mirror 21, travels in the reverse direction onthe same optical path (the optical path P2), and is transmitted throughthe half mirror surface 31.

A part of the measurement light L0 reflected by the half mirror surface31 and the remaining part of the measurement light L0 transmittedthrough the half mirror surface 31 become the measurement light L1 thatis the interference light and the measurement light L1 is transmittedthrough the dichroic mirror surface 35 and is emitted from the beamsplitter unit 3 to the outside of the optical module 1E through theoptical surface 36 d.

Further, when the laser light L10 emitted from the light source 5 istransmitted through the half mirror 8 and is incident to the beamsplitter unit 3 through the optical surface 36 e, the laser light L10 isreflected by the dichroic mirror surface 35 and travels toward the halfmirror surface 31. A part of the laser light L10 is sequentiallyreflected by the half mirror surface 31 and the total reflection mirrorsurface 32 and travels toward the mirror surface 11 a of the movablemirror 11. Then, a part of the laser light L10 is reflected by themirror surface 11 a of the movable mirror 11, travels in the reversedirection on the same optical path (an optical path P3), and isreflected by the half mirror surface 31.

Meanwhile, the remaining part of the laser light L10 is transmittedthrough the half mirror surface 31, passes through the first opticalfunction portion 17, is further transmitted through the support body 22,and travels toward the mirror surface 21 a of the fixed mirror 21. Then,the remaining part of the laser light L10 is reflected by the mirrorsurface 21 a of the fixed mirror 21, travels in the reverse direction onthe same optical path (an optical path P4), and is transmitted throughthe half mirror surface 31.

A part of the laser light L10 reflected by the half mirror surface 31and the remaining part of the laser light L10 transmitted through thehalf mirror surface 31 become the laser light L11 that is theinterference light and the laser light L11 is reflected by the dichroicmirror surface 35 and is emitted from the beam splitter unit 3 throughthe optical surface 36 e. The laser light L11 emitted from the beamsplitter unit 3 is reflected by the half mirror 8, is incident to thephotodetector 6, and is detected by the photodetector 6.

[Operation and Effect]

According to the optical module 1E, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1E, the beam splitter unit 3 constitutes theinterference optical system I2 for the laser light L10 along with themovable mirror 11 and the fixed mirror 21. Accordingly, since the laserlight L11 that is the interference light of the laser light L10 isdetected, it is possible to highly accurately measure the position ofthe mirror surface 11 a of the movable mirror 11. Further, the beamsplitter unit 3 constitutes the interference optical system I1 for themeasurement light L0 and the interference optical system I2 for thelaser light L10 along with the movable mirror 11 and the fixed mirror21. For that reason, it is possible to decrease the number of parts ofthe mirror unit 2.

Modified Example of Fifth Embodiment

As illustrated in (a) of FIG. 13 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Eillustrated in (a) of FIG. 13 , the ceiling wall 243 of the package 24is provided with an opening 243 b through which the optical paths P1 andP3 pass and an opening 243 c through which the optical paths P2 and P4pass. Each of the openings 243 b and 243 c penetrates the ceiling wall243 in the Z-axis direction. The beam splitter unit 3 is supported bythe ceiling wall 243 while blocking each of the openings 243 b and 243c. Specifically, the beam splitter unit 3 is fixed to the surface 243 aof the ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical paths P1 and P3 pass and the opening 243 cthrough which the optical paths P2 and P4 pass. Furthermore, in theoptical module 1E illustrated in (a) of FIG. 13 , the ceiling wall 243may not have optical transparency with respect to the measurement lightL0 and the laser light L10. Further, when the optical resin 4 does notenter each of the openings 243 b and 243 c, a resin that does not haveoptical transparency with respect to the measurement light L0 and thelaser light L10 may be used instead of the optical resin 4. Further, theceiling wall 243 of the package 24 may be provided with one openingthrough which the plurality of optical paths P1, P2, P3, and P4 pass.

Further, as illustrated in (b) of FIG. 13 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Eillustrated in (b) of FIG. 13 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to the innersurface of the concave portion 271 a by the optical resin 4 while a partof the beam splitter unit 3 is disposed in the concave portion 271 aformed in the wall portion 271 of the support structure 27. The wallportion 271 faces the ceiling wall 243 in the Z-axis direction and theconcave portion 271 a is opened to the side opposite to the ceiling wall243 in the Z-axis direction. The bottom surface of the concave portion271 a is provided with one opening 271 b through which the plurality ofoptical paths P1, P2, P3, and P4 pass. According to such aconfiguration, since the support structure 27 supporting the beamsplitter unit 3 is provided separately from the package 24, the degreeof freedom of the layout of the beam splitter unit 3 can be improved.Furthermore, when the optical resin 4 does not enter the opening 271 b,a resin that does have optical transparency with respect to themeasurement light L0 and the laser light L10 may be used instead of theoptical resin 4.

Sixth Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 14 , an optical module 1F is mainly differentfrom the optical module 1A illustrated in FIG. 1 in that the beamsplitter unit 3 constitutes an interference optical system I1 for themeasurement light L0 and an interference optical system I2 for the laserlight L10 along with the movable mirror 11 and the fixed mirror 21. Theoptical module 1F includes a photodetector 9 in addition to the lightsource 5, the photodetector 6, and the circuit board 7. Thephotodetector 9 detects the measurement light L1 (the interference lightof the measurement light L1) emitted from the interference opticalsystem I1. The photodetector 9 is configured as, for example, aphotodiode or the like. The light source 5, the plurality ofphotodetectors 6 and 9, and the mirror unit 2 are mounted on the samecircuit board 7.

The beam splitter unit 3 includes a half mirror surface 31, a totalreflection mirror surface 32, a dichroic mirror surface 35, a halfmirror surface 37, a total reflection mirror surface 38, and a pluralityof optical surfaces 33 a, 33 b, 33 c, 33 d, 33 e, 33 f, 33 g, and 33 h.The beam splitter unit 3 is configured by bonding a plurality of opticalblocks. The half mirror surface 37 is formed by, for example, adielectric multilayer. The total reflection mirror surface 38 is formedby, for example, a metal film.

The optical surface 33 a is, for example, a surface perpendicular to theZ-axis direction and overlaps the mirror surface 21 a of the fixedmirror 21 when viewed from the Z-axis direction. The half mirror surface31 is, for example, a surface inclined by 45° with respect to theoptical surface 33 a and overlaps the mirror surface 21 a of the fixedmirror 21 when viewed from the Z-axis direction. The half mirror surface31 is located between the optical surface 33 a and the mirror surface 21a of the fixed mirror 21 in the Z-axis direction. The total reflectionmirror surface 32 is a surface parallel to the half mirror surface 31,overlaps the mirror surface 11 a of the movable mirror 11 when viewedfrom the Z-axis direction, and overlaps the half mirror surface 31 whenviewed from the X-axis direction.

The optical surface 33 b is a surface parallel to the optical surface 33a and overlaps the mirror surface 11 a of the movable mirror 11 whenviewed from the Z-axis direction. The optical surface 33 b is locatedbetween the total reflection mirror surface 32 and the mirror surface 11a of the movable mirror 11 in the Z-axis direction. The optical surface33 c is a surface parallel to the optical surface 33 a and overlaps themirror surface 21 a of the fixed mirror 21 when viewed from the Z-axisdirection. The optical surface 33 c is located between the half mirrorsurface 31 and the mirror surface 21 a of the fixed mirror 21 in theZ-axis direction. The optical surface 33 d is a surface perpendicular tothe optical surface 33 a and overlaps the half mirror surface 31 whenviewed from the X-axis direction. The optical surface 33 d is located atthe side opposite to the total reflection mirror surface 32 with respectto the half mirror surface 31 in the X-axis direction.

The optical surface 33 e is a plane parallel to the optical surface 33 dand overlaps the optical surface 33 d when viewed from the X-axisdirection. The optical surface 33 e is located at the side opposite tothe half mirror surface 31 with respect to the optical surface 33 d inthe X-axis direction. The dichroic mirror surface 35 is, for example, asurface inclined by 45° with respect to the optical surface 33 e,overlaps the photodetector 9 when viewed from the Z-axis direction, andoverlaps the optical surface 33 e when viewed from the X-axis direction.The dichroic mirror surface 35 is located at the side opposite to thehalf mirror surface 31 with respect to the optical surface 33 e in theX-axis direction. The half mirror surface 37 is a surface parallel tothe dichroic mirror surface 35, overlaps the photodetector 6 when viewedfrom the Z-axis direction, and overlaps the dichroic mirror surface 35when viewed from the X-axis direction. The half mirror surface 37 islocated at the side opposite to the optical surface 33 e with respect tothe dichroic mirror surface 35 in the X-axis direction. The totalreflection mirror surface 38 is a surface parallel to the dichroicmirror surface 35, overlaps the light source 5 when viewed from theZ-axis direction, and overlaps the half mirror surface 37 when viewedfrom the X-axis direction. The total reflection mirror surface 38 islocated at the side opposite to the dichroic mirror surface 35 withrespect to the half mirror surface 37 in the X-axis direction.

The optical surface 33 f is a surface parallel to the optical surface 33a and overlaps the photodetector 9 when viewed from the Z-axisdirection. The optical surface 33 f is located between the dichroicmirror surface 35 and the photodetector 9 in the Z-axis direction. Theoptical surface 33 g is a surface parallel to the optical surface 33 aand overlaps the photodetector 6 when viewed from the Z-axis direction.The optical surface 33 g is located between the half mirror surface 37and the photodetector 6 in the Z-axis direction. The optical surface 33h is a surface parallel to the optical surface 33 a and overlaps thelight source 5 when viewed from the Z-axis direction. The opticalsurface 33 h is located between the total reflection mirror surface 38and the light source 5 in the Z-axis direction.

In the optical module 1F with the above-described configuration, whenthe measurement light L0 is incident from the outside of the opticalmodule 1F to the beam splitter unit 3 through the optical surface 33 a,a part of the measurement light L0 is sequentially reflected by the halfmirror surface 31 and the total reflection mirror surface 32 and travelstoward the mirror surface 11 a of the movable mirror 11. Then, a part ofthe measurement light L0 is reflected by the mirror surface 11 a of themovable mirror 11, travels in the reverse direction on the same opticalpath (the optical path P1), and is transmitted through the half mirrorsurface 31.

Meanwhile, the remaining part of the measurement light L0 is transmittedthrough the half mirror surface 31, passes through the first opticalfunction portion 17, is further transmitted through the support body 22,and travels toward the mirror surface 21 a of the fixed mirror 21. Then,the remaining part of the measurement light L0 is reflected by themirror surface 21 a of the fixed mirror 21, travels in the reversedirection on the same optical path (the optical path P2), and isreflected by the half mirror surface 31.

A part of the measurement light L0 transmitted through the half mirrorsurface 31 and the remaining part of the measurement light L0 reflectedby the half mirror surface 31 become the measurement light L1 that isthe interference light and the measurement light L1 is reflected by thedichroic mirror surface 35, is incident to the photodetector 9, and isdetected by the photodetector 9.

Further, when the laser light L10 emitted from the light source 5 isincident to the beam splitter unit 3 through the optical surface 33 h,the laser light L10 is reflected by the total reflection mirror surface38, is sequentially transmitted through the half mirror surface 37 andthe dichroic mirror surface 35, and travels toward the half mirrorsurface 31. A part of the laser light L10 is transmitted through thehalf mirror surface 31, is reflected by the total reflection mirrorsurface 32, and travels toward the mirror surface 11 a of the movablemirror 11. Then, a part of the laser light L10 is reflected by themirror surface 11 a of the movable mirror 11, travels in the reversedirection on the same optical path (the optical path P3), and istransmitted through the half mirror surface 31.

Meanwhile, the remaining part of the laser light L10 is reflected by thehalf mirror surface 31, passes through the first optical functionportion 17, is further transmitted through the support body 22, andtravels toward the mirror surface 21 a of the fixed mirror 21. Then, theremaining part of the laser light L10 is reflected by the mirror surface21 a of the fixed mirror 21, travels in the reverse direction on thesame optical path (the optical path P4), and is reflected by the halfmirror surface 31.

A part of the laser light L10 transmitted through the half mirrorsurface 31 and the remaining part of the laser light L10 reflected bythe half mirror surface 31 become the laser light L11 that is heinterference light and the laser light L11 is transmitted through thedichroic mirror surface 35, is reflected by the half mirror surface 37,is incident to the photodetector 6, and is detected by the photodetector6.

[Operation and Effect]

According to the optical module 1F, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1F, the beam splitter unit 3 constitutes theinterference optical system I2 for the laser light L10 along with themovable mirror 11 and the fixed mirror 21. Accordingly, since the laserlight L11 that is the interference light of the laser light L10 isdetected, it is possible to highly accurately measure the position ofthe mirror surface 11 a of the movable mirror 11. Further, the beamsplitter unit 3 constitutes the interference optical system I1 for themeasurement light L0 and the interference optical system I2 for thelaser light L10 along with the movable mirror 11 and the fixed mirror21. For that reason, it is possible to decrease the number of parts ofthe mirror unit 2.

[Modified Example of Sixth Embodiment]

As illustrated in (a) of FIG. 15 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Fillustrated in (a) of FIG. 15 , the ceiling wall 243 of the package 24is provided with an opening 243 b through which the optical paths P1 andP3 pass and an opening 243 c through which the optical paths P2 and P4pass. Each of the openings 243 b and 243 c penetrates the ceiling wall243 in the Z-axis direction. The beam splitter unit 3 is supported bythe ceiling wall 243 while blocking each of the openings 243 b and 243c. Specifically, the beam splitter unit 3 is fixed to the surface 243 aof the ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical paths P1 and P3 pass and the opening 243 cthrough which the optical paths P2 and P4 pass. Furthermore, in theoptical module 1F illustrated in (a) of FIG. 15 , the ceiling wall 243may not have optical transparency with respect to the measurement lightL0 and the laser light L10. Further, when the optical resin 4 does notenter each of the openings 243 b and 243 c, a resin that does not haveoptical transparency with respect to the measurement light L0 and thelaser light L10 may be used instead of the optical resin 4. Further, theceiling wall 243 of the package 24 may be provided with one openingthrough which the plurality of optical paths P1, P2, P3, and P4 pass.

Further, as illustrated in (b) of FIG. 15 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Fillustrated in (b) of FIG. 15 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to the innersurface of the concave portion 271 a by the optical resin 4 while a partof the beam splitter unit 3 is disposed in the concave portion 271 aformed in the wall portion 271 of the support structure 27. The wallportion 271 faces the ceiling wall 243 in the Z-axis direction and theconcave portion 271 a is opened to the side opposite to the ceiling wall243 in the Z-axis direction. The bottom surface of the concave portion271 a is provided with one opening 271 b through which the plurality ofoptical paths P1, P2, P3, and P4 pass. According to such aconfiguration, since the support structure 27 supporting the beamsplitter unit 3 is provided separately from the package 24, the degreeof freedom of the layout of the beam splitter unit 3 can be improved.Furthermore, when the optical resin 4 does not enter the opening 271 b,a resin that does not have optical transparency with respect to themeasurement light L0 and the laser light L10 may be used instead of theoptical resin 4.

Seventh Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 16 , an optical module 1G is mainly differentfrom the optical module 1E illustrated in FIG. 12 in that the beamsplitter unit 3 constitutes an interference optical system I2 for thelaser light L10 along with the movable mirror 11 and a fixed mirror (asecond fixed mirror) 200. The fixed mirror 200 includes a mirror surface200 a following a plane parallel to the main surface 12 a of the base12. The position of the fixed mirror 200 with respect to the base 12 isfixed. The mirror surface 200 a of the fixed mirror 200 faces one side(the side of the beam splitter unit 3) in the Z-axis direction similarlyto the mirror surface 11 a of the movable mirror 11 and the mirrorsurface 21 a of the fixed mirror 21. The fixed mirror 200 is disposed onthe surface 22 c of the support body 22 so as to be located inside theopening 23 b formed in the sub-mount 23. The fixed mirror 200 isdisposed at the other side of the movable mirror 11 (the side oppositeto the fixed mirror 21) in the X-axis direction when viewed from theZ-axis direction. The fixed mirror 200 overlaps the second opticalfunction portion 18 of the optical device 10 when viewed from the Z-axisdirection. Furthermore, in the mirror unit 2, a part of the optical pathP4 between the beam splitter unit 3 and the fixed mirror 200 is disposedin the airtight space S in addition to the movable mirror 11, the driveunit 13, a part of the optical path P1, and a part of the optical pathP2.

The beam splitter unit 3 includes a plurality of half mirror surfaces 31a and 31 b, a dichroic mirror surface 35, a total reflection mirrorsurface 38, and a plurality of optical surfaces 33 a, 33 b, 33 c, 33 d,33 e, and 33 f. The beam splitter unit 3 is configured by bonding aplurality of optical blocks.

The optical surface 33 a is, for example, a surface perpendicular to theZ-axis direction and overlaps the mirror surface 21 a of the fixedmirror 21 when viewed from the Z-axis direction. The half mirror surface31 a is, for example, a surface inclined by 45° with respect to theoptical surface 33 a and overlaps the mirror surface 21 a of the fixedmirror 21 when viewed from the Z-axis direction. The half mirror surface31 a is located between the optical surface 33 a and the mirror surface21 a of the fixed mirror 21 in the Z-axis direction. The half mirrorsurface 31 b is a surface parallel to the half mirror surface 31 a,overlaps the mirror surface 11 a of the movable mirror 11 when viewedfrom the Z-axis direction, and overlaps the half mirror surface 31 awhen viewed from the X-axis direction.

The optical surface 33 b is a surface parallel to the optical surface 33a and overlaps the mirror surface 11 a of the movable mirror 11 whenviewed from the Z-axis direction. The optical surface 33 b is locatedbetween the half mirror surface 31 b and the mirror surface 11 a of themovable mirror 11 in the Z-axis direction. The optical surface 33 c is asurface parallel to the optical surface 33 a and overlaps the mirrorsurface 21 a of the fixed mirror 21 when viewed from the Z-axisdirection. The optical surface 33 c is located between the half mirrorsurface 31 a and the mirror surface 21 a of the fixed mirror 21 in theZ-axis direction.

The optical surface 33 d is, for example, a surface perpendicular to theZ-axis direction and overlaps the light source 5 and the mirror surface11 a of the movable mirror 11 when viewed from the Z-axis direction. Theoptical surface 33 d is located at the side opposite to the mirrorsurface 11 a of the movable mirror 11 with respect to the half mirrorsurface 31 b in the Z-axis direction. The total reflection mirrorsurface 38 is a surface parallel to the half mirror surface 31 a,overlaps the mirror surface 200 a of the fixed mirror 200 when viewedfrom the Z-axis direction, and overlaps the half mirror surface 31 bwhen viewed from the X-axis direction. The optical surface 33 e is asurface parallel to the optical surface 33 d and overlaps the mirrorsurface 200 a of the fixed mirror 200 when viewed from the Z-axisdirection. The optical surface 33 e is located between the totalreflection mirror surface 38 and the mirror surface 200 a of the fixedmirror 200 in the Z-axis direction.

The dichroic mirror surface 35 is a surface parallel to the half mirrorsurface 31 a and overlaps the photodetector 6 when viewed from theZ-axis direction. The dichroic mirror surface 35 is located at the sideopposite to the half mirror surface 31 b with respect to the half mirrorsurface 31 a in the X-axis direction. The optical surface 33 f is, forexample, a surface perpendicular to the Z-axis direction and overlapsthe photodetector 6 when viewed from the Z-axis direction. The opticalsurface 33 f is located between the dichroic mirror surface 35 and thephotodetector 6 in the Z-axis direction.

In the optical module 1G with the above-described configuration, whenthe measurement light L0 is incident from the outside of the opticalmodule 1G to the beam splitter unit 3 through the optical surface 33 a,a part of the measurement light L0 is sequentially reflected by the halfmirror surface 31 a and the half mirror surface 31 b and travels towardthe mirror surface 11 a of the movable mirror 11. Then, a part of themeasurement light L0 is reflected by the mirror surface 11 a of themovable mirror 11, travels in the reverse direction on the same opticalpath (the optical path P1), and is transmitted through the half mirrorsurface 31 a.

Meanwhile, the remaining part of the measurement light L0 is transmittedthrough the half mirror surface 31 a, passes through the first opticalfunction portion 17, is further transmitted through the support body 22,and travels toward the mirror surface 21 a of the fixed mirror 21. Then,the remaining part of the measurement light L0 is reflected by themirror surface 21 a of the fixed mirror 21, travels in the reversedirection on the same optical path (the optical path P2), and isreflected by the half mirror surface 31 a.

A part of the measurement light L0 transmitted through the half mirrorsurface 31 a and the remaining part of the measurement light L0reflected by the half mirror surface 31 a become the measurement lightL1 that is the interference light and the measurement light L1 istransmitted through the dichroic mirror surface 35 and is emitted fromthe beam splitter unit 3 to the outside of the optical module 1G.

Further, when the laser light L10 emitted from the light source 5 isincident to the beam splitter unit 3 through the optical surface 33 d, apart of the laser light L10 is transmitted through the half mirrorsurface 31 b and travels toward the mirror surface 11 a of the movablemirror 11. Then, a part of the laser light L10 is reflected by themirror surface 11 a of the movable mirror 11, travels in the reversedirection on the same optical path (the optical path P3), and isreflected by the half mirror surface 31 b.

Meanwhile, the remaining part of the laser light L10 is sequentiallyreflected by the half mirror surface 31 b and the total reflectionmirror surface 38 and travels toward the mirror surface 200 a of thefixed mirror 200. Then, the remaining part of the laser light L10 isreflected by the mirror surface 200 a of the fixed mirror 200, travelsin the reverse direction on the same optical path (the optical path P4),and is transmitted through the half mirror surface 31 b.

A part of the laser light L10 reflected by the half mirror surface 31 band the remaining part of the laser light L10 transmitted through thehalf mirror surface 31 b become the laser light L11 that is theinterference light and the laser light L11 is transmitted through thehalf mirror surface 31 a, is reflected by the dichroic mirror surface35, is incident to the photodetector 6, and is detected by thephotodetector 6.

[Operation and Effect]

According to the optical module 1G, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

In the optical module 1G, the beam splitter unit 3 constitutes theinterference optical system I2 for the laser light L10 along with themovable mirror 11 and the fixed mirror 200. Accordingly, since the laserlight L11 that is the interference light of the laser light L10 isdetected, it is possible to highly accurately measure the position ofthe mirror surface 11 a of the movable mirror 11. Further, the mirrorsurface 200 a of the fixed mirror 200 faces one side in the Z-axisdirection similarly to the mirror surface 21 a of the fixed mirror 21.For that reason, the height of the mirror unit 2 in the Z-axis directioncan be suppressed as compared with, for example, a positionalrelationship in which the mirror surface 11 a of the movable mirror 11and the mirror surface 200 a of the fixed mirror 200 are orthogonal toeach other. Moreover, a part of the optical path P4 between the beamsplitter unit 3 and the fixed mirror 200 is disposed in the airtightspace S similarly to a part of the optical path P2 between the beamsplitter unit 3 and the fixed mirror 21 in addition to the optical pathP1 between the beam splitter unit 3 and the movable mirror 11.Accordingly, it is possible to suppress the width of the mirror unit 2in a direction (in the optical module 1G, the X-axis direction)perpendicular to the Z-axis direction.

[Modified Example of Seventh Embodiment]

As illustrated in (a) of FIG. 17 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Gillustrated in (a) of FIG. 17 , the ceiling wall 243 of the package 24is provided with an opening 243 b through which the optical paths P1 andP3 pass, an opening 243 c through which the optical path P2 passes, andan opening 243 d through which the optical path P4 passes. Each of theopenings 243 b, 243 c, and 243 d penetrates the ceiling wall 243 in theZ-axis direction. The beam splitter unit 3 is supported by the ceilingwall 243 while blocking each of the openings 243 b, 243 c, and 243 d.Specifically, the beam splitter unit 3 is fixed to the surface 243 a ofthe ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical paths P1 and P3 pass, the opening 243 cthrough which the optical path P2 passes, and the opening 243 d throughwhich the optical path P3 passes. Furthermore, in the optical module 1Gillustrated in (a) of FIG. 17 , the ceiling wall 243 may not haveoptical transparency with respect to the measurement light L0 and thelaser light L10. Further, when the optical resin 4 does not enter eachof the openings 243 b, 243 c, and 243 d, a resin that does not haveoptical transparency with respect to the measurement light L0 and thelaser light L10 may be used instead of the optical resin 4. Further, theceiling wall 243 of the package 24 may be provided with one openingthrough which the plurality of optical paths P1, P2, P3, and P4 pass.

Further, as illustrated in (b) of FIG. 17 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Gillustrated in (b) of FIG. 17 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to the innersurface of the concave portion 271 a by the optical resin 4 while a partof the beam splitter unit 3 is disposed in the concave portion 271 aformed in the wall portion 271 of the support structure 27. The wallportion 271 faces the ceiling wall 243 in the Z-axis direction and theconcave portion 271 a is opened to the side opposite to the ceiling wall243 in the Z-axis direction. The bottom surface of the concave portion271 a is provided with one opening 271 b through which the plurality ofoptical paths P1, P2, P3, and P4 pass. According to such aconfiguration, since the support structure 27 supporting the beamsplitter unit 3 is provided separately from the package 24, the degreeof freedom of the layout of the beam splitter unit 3 can be improved.Furthermore, when the optical resin 4 does not enter the opening 271 b,a resin that does not have optical transparency with respect to themeasurement light L0 and the laser light L10 may be used instead of theoptical resin 4.

Eighth Embodiment

[Configuration of Optical Module]

As illustrated in FIG. 18 , an optical module 1H is mainly differentfrom the optical module 1A illustrated in FIG. 1 in that the concaveportion 22 b is not formed in the support body 22. In the optical module1H, the base 12 of the optical device 10 is fixed to the inner surfaceof the bottom wall 241 of the package 24. In the optical module 1H, theoptical device 10 is disposed so that the main surface 12 a of the base12 faces the inner surface of the ceiling wall 243 and the main surface12 b of the base 12 faces the inner surface of the bottom wall 241.

In the optical module 1H, an opening 51 a is formed in a regioncorresponding to the movable mirror 11 and the drive unit 13 in thesupport layer 51 of the base 12. Accordingly, the contact of the movablemirror 11 and the drive unit 13 with respect to the support body 22 whenthe movable mirror 11 is moved along the Z-axis direction is prevented.A metal film forming the movable mirror 11 is formed on a surface at theside of the main surface 12 a in the main body 111. A metal film formingthe fixed mirror 21 is formed in the entire region of the surface 22 cof the support body 22.

In the optical module 1H with the above-described configuration, themeasurement light L1 that is the interference light of the measurementlight L0 can be obtained similarly to the optical module 1A illustratedin FIG. 1 . Furthermore, the optical module 1H includes a measurementlight incident unit 300 and a measurement light emission unit 400. Themeasurement light incident unit 300 is disposed so that the measurementlight L0 is incident from the outside to the interference optical systemI1. The measurement light incident unit 300 includes, for example, anoptical fiber, a collimating lens, and the like. The measurement lightemission unit 400 is disposed so that the measurement light L1 (theinterference light of the measurement light L0) is emitted from theinterference optical system I1 to the outside. The measurement lightemission unit 400 includes, for example, an optical fiber, a collimatinglens, and the like. Accordingly, it is possible to obtain the FTIRincluding the measurement light incident unit 300 and the measurementlight emission unit 400.

[Operation and Effect]

According to the optical module 1H, for the same reason as theabove-described optical module 1A, it is possible to suppressdeterioration in the movable performance of the movable mirror 11 and anincrease in the size of the entire module while enlarging the mirrorsurface 11 a of the movable mirror 11.

[Modified Example of Eighth Embodiment]

As illustrated in (a) of FIG. 19 , the airtight space S may be formed bythe package 24 and the beam splitter unit 3. In the optical module 1Hillustrated in (a) of FIG. 19 , the ceiling wall 243 of the package 24is provided with an opening 243 b through which the optical path P1passes and an opening 243 c through which the optical path P2 passes.Each of the openings 243 b and 243 c penetrates the ceiling wall 243 inthe Z-axis direction. The beam splitter unit 3 is supported by theceiling wall 243 while blocking each of the openings 243 b and 243 c.Specifically, the beam splitter unit 3 is fixed to the surface 243 a ofthe ceiling wall 243 by the optical resin 4. According to such aconfiguration, both of the formation of the airtight space S and thesupport of the beam splitter unit 3 can be realized by the simplepackage 24 including the ceiling wall 243 provided with the opening 243b through which the optical path P1 passes and the opening 243 c throughwhich the optical path P2 passes. Furthermore, in the optical module 1Hillustrated in (a) of FIG. 19 , the ceiling wall 243 may not haveoptical transparency with respect to the measurement light L0. Further,when the optical resin 4 does not enter each of the openings 243 b and243 c, a resin that does not have optical transparency with respect tothe measurement light L0 may be used instead of the optical resin 4.Further, the ceiling wall 243 of the package 24 may be provided with oneopening through which the plurality of optical paths P1 and P2 pass.

Further, as illustrated in (b) of FIG. 19 , the support structure 27supporting the beam splitter unit 3 may be provided separately from thepackage 24 forming the airtight space S. In the optical module 1Hillustrated in (b) of FIG. 19 , the beam splitter unit 3 is supported bythe support structure 27 while being separated from the ceiling wall243. Specifically, the beam splitter unit 3 is fixed to the innersurface of the concave portion 271 a by the optical resin 4 while a partof the beam splitter unit 3 is disposed in the concave portion 271 aformed in the wall portion 271 of the support structure 27. The wallportion 271 faces the ceiling wall 243 in the Z-axis direction and theconcave portion 271 a is opened to the side opposite to the ceiling wall243 in the Z-axis direction. The bottom surface of the concave portion271 a is provided with one opening 271 b through which the plurality ofoptical paths P1 and P2 pass. According to such a configuration, sincethe support structure 27 supporting the beam splitter unit 3 is providedseparately from the package 24, the degree of freedom of the layout ofthe beam splitter unit 3 can be improved. Furthermore, when the opticalresin 4 does not enter the opening 271 b, a resin that does not haveoptical transparency with respect to the measurement light L0 may beused instead of the optical resin 4.

[Modified Examples]

As described above, the first to eighth embodiments of the presentdisclosure have been described, but the present disclosure is notlimited to the above-described embodiments. For example, the materialand shape of each component are not limited to the materials and shapesdescribed above and various materials and shapes can be adopted. As anexample, the material of the support body 22 is not limited as long asthe support body corrects the optical path difference between theoptical path P1 and the optical path P2 so that a difference between theoptical path length of the optical path P1 (the optical path lengthconsidering the refractive index of each medium through which theoptical path P1 passes) and the optical path length of the optical pathP2 (the optical path length considering the refractive index of eachmedium through which the optical path P2 passes) decreases. The materialof the support body 22 may be silicon, chalcogenide, or the like inaddition to glass.

Further, the optical modules 1A, 1B, 1C, 1D, 1E, 1F, and 1G may includethe measurement light incident unit 300 and the measurement lightemission unit 400. In contrast, the optical module 1H may not includethe measurement light incident unit 300 and the measurement lightemission unit 400.

Further, the drive unit 13 of the optical device 10 is not limited tothe above-described configuration as long as the drive unit can move themovable mirror 11 along a direction perpendicular to the main surface 12a of the base 12. As an example, the first elastic support portion 14and the second elastic support portion 15 may have a symmetricalstructure with respect to a plane passing through the center of themovable mirror 11 and perpendicular to the X-axis direction. Further,the first elastic support portion 14 and the second elastic supportportion 15 may have a symmetrical structure with respect to a planepassing through the center of the movable mirror 11 and perpendicular tothe Y-axis direction. Further, the drive unit 13 may include three ormore elastic support portions elastically supporting the movable mirror11. Furthermore, the actuator 16 is not limited to the electrostaticactuator and may be configured as, for example, a piezoelectricactuator, an electromagnetic actuator, or the like.

Further, in the optical modules 1E, 1F, and 1G, a filter cutting lightin a wavelength range including a center wavelength of the laser lightL10 may be disposed on the optical path along which the laser light L10does not travel and the measurement light L0 travels. As an example, inthe optical module 1E illustrated in FIG. 12 , the above-describedfilter may be disposed at the front stage of the optical surface 33 a.In this case, it is possible to prevent the measurement light L0 frombecoming noise in the detection of the laser light L11 that is theinterference light of the laser light L10.

The drive unit 13 of the optical device 10 illustrated in FIGS. 4 to 6and FIGS. 12 to 19 has the same configuration as that of the drive unit13 of the optical device 10 illustrated in FIGS. 1 to 3 and the driveunit 13 of the optical device 10 illustrated in FIGS. 7 to 11 has theconfiguration illustrated in FIG. 20 unlike the drive unit 13 of theoptical device 10 illustrated in FIGS. 1 to 3 . In the optical device 10illustrated in FIG. 20 , the end portion 141 b at the side opposite tothe movable mirror 11 in each of the pair of first levers 141 isconnected to the base 12 through the torsion bar 144 and the end portion151 b at the side opposite to the movable mirror 11 in each of the pairof third levers 151 is connected to the base 12 through the torsion bar154. That is, in the optical device 10 illustrated in FIG. 20 , the pairof second levers 142 and the pair of fourth levers 152 are not provided.In this way, in the optical device 10 illustrated in FIG. 20 , thestructure of the first elastic support portion 14 and the second elasticsupport portion 15 is simplified.

Each configuration in one embodiment or modified example described abovecan be arbitrarily applied to each configuration in another embodimentor modified example.

REFERENCE SIGNS LIST

1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H: optical module, 2: mirror unit, 3: beamsplitter unit, 5: light source, 6: photodetector, 11: movable mirror, 11a: mirror surface, 12: base, 12 a: main surface, 13: drive unit, 21:fixed mirror (first fixed mirror), 21 a: mirror surface, 22: supportbody, 22 c: surface, 24: package, 27: support structure, 29: supportwall (wall), 29 d, 29 e: opening, 50: SOI substrate, 111: main body(movable portion), 112: wall portion (movable portion), 113, 114:bracket (movable portion), 200: fixed mirror (second fixed mirror), 200a: mirror surface, 243: ceiling wall (wall), 243 b, 243 c: opening, I1:interference optical system (first interference optical system), I2:interference optical system (second interference optical system), L0,L1: measurement light, L10, L11: laser light, P1: optical path (firstoptical path), P2: optical path (second optical path), P4: optical path,S: airtight space.

The invention claimed is:
 1. A mirror unit comprising: a base whichincludes a first main surface and a second main surface opposite eachother; a movable mirror which includes a mirror surface following aplane parallel to the first main surface and is supported by the base soas to be movable along a first direction perpendicular to the first mainsurface; a drive unit which includes at least a portion connected to thebase and the movable mirror, and moves the movable mirror along thefirst direction; a first member which includes a first surface fixed tothe first main surface and a first recess formed on the first surface soas to correspond to the movable mirror and the drive unit; and a secondmember which includes a second surface fixed to the second main surfaceand a second recess formed on the second surface so as to correspond tothe movable mirror and the drive unit.
 2. The mirror unit according toclaim 1, wherein an airtight space is formed by the base, the firstmember and the second member.
 3. The mirror unit according to claim 1,wherein the first recess is formed on the first surface so as to expandtoward the movable mirror and the drive unit.
 4. The mirror unitaccording to claim 1, wherein the second member has opticaltransparency.
 5. The mirror unit according to claim 1, wherein the baseis provided with a plurality of electrode pads, and the plurality ofelectrode pads are arranged along a longitudinal direction of the base.6. The mirror unit according to claim 5, wherein the plurality ofelectrode pads are arranged along the longitudinal direction in portionsof the base on both sides of the movable mirror and the drive unit. 7.The mirror unit according to claim 1, wherein the drive unit includes afirst comb electrode provided on the base side and a second combelectrode provided on the movable mirror side, and each of a pluralityof comb fingers of the first comb electrode is located between each of aplurality of comb fingers of the second comb electrode.